It is narrated from Hazrat Malik bin Huwairith that we, a group of young men who were almost of the same age, came to the service of the Prophet (peace be upon him) and stayed with him for twenty nights. The Prophet (peace be upon him) was very kind and soft-hearted. He sensed that now we were longing to meet our families. He asked us whom we had left behind at home. The Prophet (peace be upon him) said: Now you should return to your families, stay with them, teach them, and inform them that when the time for prayer comes, one person should give the call to prayer (adhan), and the eldest among you should lead the prayer (imam).