The last words of the Buddha - Mahaprinibbana Sutta

It is important to understand the destination if you would take the most direct path from start to finish.  We will first understand the object of training, and in the final lessons understand their applications.  Before performing Karma Yoga, it is necessary to have trained in Hatha Yoga, which requires understanding Bhakti Yoga, which in turn requires a contextual foundation in Jnana Yoga.
In reading the Vedas, it is important to understand that there are an almost infinite combination of meanings which can be derived from them: each syllable has meaning as a word, and with multiple translations and connotations. Combining these syllables into compound words results in new meaning: water+melon is different than watermelon.  Thus, any translation is problematic: it is therefore inappropriate to translate the Vedas, except for particular and specific communications, showing them in a particular light required for an occasion or the given audience.  Like cutting a diamond can alter its purpose and effect, the roughness of the Vedas hides an unspeakable beauty.
The last words of the Buddha, like any of the Vedas, are difficult to translate. The Buddha frequently employed double meanings and puns to his words, frequently to dramatic effect, sometimes even for humorous effect.  Though there is certainly no humorous intention to the words he uttered as he lay dying in agony, his layered words (however eloquent in his native language) do not easily render into English with the same double meaning.  
It is important to note the references to Shiva, both direct and indirect.  These are presented later.  But notice here that the formulaic prose sung, especially when combined with the form of repetition represented by those attending and assisting the dying, echoes a sacrificial practice described at the beginning of the Khandogya Upanishad, as connected to the Samaveda, regarding the pronunciation of the udgitha (om, or pranava), which is invoked to fulfill the purpose of the sacrifice.  The Rik is represented by speech, Saman by breath, the udgitha is the Om.  Speech and breath, or Rik and Saman, form one couple.  This is echoed by how the Adhvaryu Priest (or their assistant) will give the order, the Hotri Priest will then recite or confirm (as in the sense of a quality control) the accomplishment of the one performing the order (the sacrificer), and the song of the Udgartri Priest, who combines and supports the efforts of the three Priests and the sacrificer for the satisfaction or fulfillment of the desire, the purpose of the sacrifice.
Similarly, the stanzas echo too the epics of Vishnu presented in the Puranas, representing the fulfillment of the purpose of this Avatara of the Buddha, invoking the peace Vishnu sought between the Devas and Asuras, and all beings, in assisting Shiva's victory over Maya, Kali - not by domination, but by taming, cultivating, civilizing, friendship and love, merging reality and the illusion of our perception of it into truth.  This peace in turn has the double meaning of invoking Shiva's name.  As do the numerous other invocations (Shankara, etc.).  Shiva is invoked in Shiva's role of presiding over any sacrifice.  In this case, the sacrifice of sacrificing: this is the end of religion and faith, its purpose.
And, of course, the stanzas directly reference the questions and doubt of Subhadda, who was perplexed by the various religions, the choice to worship according to doctrines of devas, or asuras.
I have attempted to combine the multiple versions told of this moment into a single rendition, so that the different perspectives, merged, better show their interconnection.  Just as a fire is shared from all directions, and we must circumambulate to observe it completely, seeing things from another's perspective, another's practice and doctrine, we must take a comprehensive view of this last sacrifice of the Buddha, in the context of his life, and purpose.

Subhadda had studied every religion and became perplexed, and so he asked the Buddha Gotama: all the religious leaders say that their doctrine, their method, their practice is the right one, the best one.  "Here there is truth, in no other doctrine is there truth," they say.  Are all of them correct?  Are none of them correct?  Are any of them correct, even partially?  Do you say in Buddhism there is truth, no other doctrine is true?  Does the Buddha teach the answers which will resolve my doubt about this?
The Buddha lay dying, in agony.  There was nothing even Ananda could do to alleviate his discomfort, or even extend his life.  The Buddha knew he would die very soon, and that he did not have time to help Subhadda understand the fallacy of his question, so he simply told Subhadda to set his question aside, as the reasoning which produced it was founded upon a false premise, and so it could not be resolved.
The Buddha said, Subhadda, you know I do not teach that my doctrine is true.  I teach no doctrine is true, though it is true there are doctrines.  This is because when I was 29 years old, I went forth, seeking, as you do, and from every teacher and leader, I heard as you did.  I learned as you did.  And since my going forth, more than 50 years have passed, and I have spoken to more teachers and leaders than you likely will.  By all this, what did I learn?  What did I find that was useful to you?  I found it was the method of my seeking which made what I heard and learned useful, even when what I heard was not true.  It is the method by which I understood the limitations of belief which will be most useful to you.
Subhadda, I learned that when we do not know the truth of something, we form beliefs; we attach to them, we possess them: we say, this is MY belief.  Having made these beliefs, and made them our own, we will insist upon them, saying they are better than other beliefs - which are also founded upon the absence of truth.  We might even delude ourselves, mistaking our beliefs for truth, saying what I believe is true.  This is why those you spoke to say, "my belief is true, no other belief is true."  They have come to think their desire for truth is satisfied by belief, by faith.  And when reality contradicts our beliefs, or others disagree, they react with aggression to protect those beliefs.  Subhadda, people will even harm one another based upon their beliefs.
So too it is when we rely on the authority of one person or another, one doctrine or another.  When we seek a teacher as an authority, we develop doctrine, and dogma.  Then there is debate and argument, then there is disagreement and doubt.  In our delusion, in our desire for truth, in this state of aggression, we harm not only one another, but ourselves.  For should we should lose our debate, or find our beliefs refuted by reality, we will sit dejected, consumed by doubt, and think not only that our beliefs are wrong, but that there is nothing true.  We then will think there is no truth at all.  Then we are defeated.
In that defeat, we might come to delude ourselves that we have triumphed when we clearly have lost - either by adopting some other belief, or by developing beliefs against reality.  In this defeat we reinforce our wrong thinking that some beliefs are superior, others are inferior - that ours are superior - when all beliefs are all simply beliefs, and none are founded upon truth, only upon the absence of it.  Faith cannot resolve our doubt of the truth.  Religion will not resolve your doubts, Subhadda.  Only logic and reason can reveal reality.
There is truth, Subhadda.  But it is not found by faith.  It is by reason and logic we understand there is no truth in any belief or doctrine. This is why I teach the method by which to find truth, the method by which to resolve doubt, but I do not teach truth.  This is why I say, whatever doctrine or discipline is devoid of this method of logic and reason will rely upon faith, result in belief, and therefore produce doubt, not reveal reality.
Now you will see why these other teachers do not practice to abandon their beliefs as I do.  Quite the opposite, in the presence of doubt, they teach the importance of faith, and train to reinforce faith, and belief.  Thus, they will always be desiring truth, they will always fear truth, they will always delude themselves as to what is true.  They will always be in doubt, and inspire doubt, instead of confidence.  Defeated, they teach contentment with faith, with doubt, they teach against challenging that doubt by giving up beliefs.  I would not have you lack confidence, Subhadda.
The Buddha said, look at me, Subhadda. Look at me and you will see the Dharma: it is me, it is Siddha-Artha, skillful work.  It is by Siddhartha you will know the Dharma.  Upon reason and fact take confidence: sacrifice your sacrificing, give up your beliefs.  What is true is beyond belief.  Belief, religion, faith - it conditions its own ending.

The Buddha sang quietly as he died,

vaya-dhamma Sankhara
app-amadena sam-padetha
[which contains simply so many layers of meaning, it is difficult to translate, and is therefore presented below in multiple renditions - translator]

This is my last breath.  Steady, now!  
As someone who is intoxicated and deluded may by vigilance cautiously walk steady
Seeing beyond the delusion of their intoxication the true nature of reality
I take my next step with my last breath

I now let fly my last breath - like the crows who eat the pinda in sraddha
As the crows eat the pinda in sraddha, Shiva Shankara, I sacrifice my last air, 

oh, weaver of the fabric of Dharma, Sankhara, maker of success
strive now toward reality step by confident step

This act of Dharma, my last breath, this duty 
honors the protector of the ashrama (playhouse) of this play (life) [play has the connotation of theater, sport, and childish recreation]

There is dissatisfaction in what is subject to decay, in life

Procure sobriety from the delusion of sensual perception
That life which causes such excessive intoxication conditions a supreme sobriety (of death)

Ananda answered, continuing the melody of the Vedas,

The self-awakened one has become entirely unbound!

Anuruddha, who stood nearby nursing the Buddha, confirmed what Ananda said, continuing the melody of the Vedas, singing

He has no in breath
He has no out breath
The one who was Such
The firm-minded one
    in seeking peace
Has succeeded?  [the term also is referencing and invoking Indra]
He completed the ends [purpose, span] of his life?

With the Buddha unbound, Indra, King of the Devas, who stood quietly nearby, together with a great number of Devas and Asuras, upon this confirmation, continuing the melody of the Vedas, singing and comforting Ananda, in his loss, that the sacrifice was successful, and answering Anuruddha,

What is conditioned and compounded comes unbound in decay
This is the nature of such things: to arise, decay, and pass away
Even as they arise, they still and grow quiet in peace (Anuruddha) and bliss (Ananda)

[which may be also understood to be a reference to the name of Shiva, completing the invocation, and Ananda's tendency to stand nearby quietly, and still, and Anuruddha's soothing palliative nursing]