Vishnu Purana 3.7 - the Yama Gita
All things that began must end, all things that are born must die: Yama is the Lord of all beings and existence itself - except for true Vaishnavas. For only Vishnu is able to control Yama. Whoever does not deviate from their duties even in severest of crisis, who does not steal the wealth of others and kill animals is undoubtedly a devotee of Lord Vishnu. Whoever bears Lord Vishnu in their heart is a devotee of Lord Vishnu. Whoever is free from all kinds of ego and illusions and always wishes well for the others with pure and peaceful heart is a devotee of Lord Vishnu. Thus those who always contemplate on Lord Vishnu don’t fear Yama's lasso, they do not fear death. Yama, Yamadoot, Yamapaash, Yamagana and even tortures of Yama are unable to hurt them.