This is a story told by His Holiness Jayendra Saraswathi Swamigal to a small gathering of devotees.
Once a person did a great penance to see Yamadharmaraja. Yama was wondering and decided to give this wonderful bhaktha his dharsan. He appeared in big buffalow in front of devotee.Lord Yama asked him why did he want to see him. The devotee told the Yama, that he had heard the stories of various asuras who have done thapas to see Brahma, Vishnu and Siva for avoiding Death.
But they have failed. So he thought it could be better to invoke Yama himself to avoid death. Yama laughed and said that he could not avoid death but he could avoid to go to hell if he uttered the name of Narayana or Siva.
Devotee insisted on avoiding death. Yama told him that he would warn him three times, to know that death is nearing him.Yama disappeared. Devotee agreed. He was happy that a warning will come from Yama and he can start uttering Nama of Narayana at the first warning itself so that he can get heaven.
After few years his hair become lost its original colour and became grey. Devotee decided to apply dye to the head so that it appeared to be black. He thought he became young and started all his materialistic enjoyments.
After sometime again he has short his original sight. He consulted an eye doctor and started wearing specks.
After some more years his teeth started falling one by one. Then he started wearing artificial teeth set. and started his usual work for more material happiness without uttering even a single nama of God.
One fine morening Yama decided to appear before him. Usually Yama takes life without appearing himself before the soul. But because of the tapas did by this devotee appeared and asked him to proceed with him
The deotee perplexed.
Yama told him that he has warned him three times,
by graying his hair,
loosing his sight and
making his teeth to fall.
But he has not uttered not even once God;s Name. However he said that he would give one minutes time for chanting nama and if God willing he may get mukthi or heaven.
Devotee realised and chanted Rama Nama as many times as possible. Perumal with all His usual Grace appeared took him and blessed him with Mukthi