Sometimes he, sallallaahu ‘alayhi wa sallam, would not ask for the details of the sin so as to cover the sinner:

Abu Umaamah (a Companion) said: 

“While we were sitting with the Prophet of Allah, sallallaahu ‘alayhi wa sallam, in the mosque, a man came in and said: ‘O Messenger of Allah, I have committed a sin that necessitates the Hadd punishment, so implement it upon me.’ The Prophet of Allah, sallallaahu ‘alayhi wa sallam, stayed silent and did not ask him anything. The man repeated: ‘O Messenger of Allah, I have committed a sin that necessitates the Hadd punishment, so implement it upon me.’ He again stayed silent, until the time for prayer came. After the prayer, the man followed the Prophet of Allah, sallallaahu ‘alayhi
wa sallam, when he left, and I followed them to hear what he would say. The man said: ‘O Messenger of Allah, I have committed a sin that necessitates the Hadd punishment, so implement it upon me.’ The Messenger of Allah, sallallaahu ‘alayhi wa sallam, said to him:‘When you left your house, did you not perform ablution well?’ The man said: ‘Yes I did, O Messenger of Allah.’ The Prophet of Allah, sallallaahu ‘alayhi wa sallam, said: ‘Then you prayed with us?’ The man said: ‘Yes, O Messenger of Allah.’ The Prophet
of Allah, sallallaahu ‘alayhi wa sallam, said: ‘Then Allah has forgiven your sin.’ Or he, sallallaahu ‘alayhi wa sallam, said: ‘Your Hadd.’” (1)