Today a man came to me and asked me a question which I did not know how to answer. He said, "Tell
me, if a wealthy active man, well-equipped with arms, goes out on military expeditions with our
chiefs, and orders us to do such things as we cannot do (should we obey him?)" I replied, "By Allah, I
do not know what to reply you, except that we, were in the company of the Prophet (ﷺ) and he used to
order us to do a thing once only till we finished it. And no doubt, everyone among you will remain in
a good state as long as he obeys Allah. If one is in doubt as to the legality of something, he should ask
somebody who would satisfy him, but soon will come a time when you will not find such a man. By
Him, except Whom none has the right to be worshipped. I see that the example of what has passed of
this life (to what remains thereof) is like a pond whose fresh water has been used up and nothing
remains but muddy water."
Sahih al-Bukhari Book 56, Hadith 174
"We were traveling with the Messenger of Allah and I was riding a camel. The Messenger of Allah said to me: 'Will you sell it to me for such and such, may Allah forgive you?', I said, I said, 'Yes, it is yours, O Prophet of Allah.' He said: 'Will you sell it to me for such and such, may Allah forgive your?' I said: 'Yes, it is yours, O Prophet of "Allah.' He said: 'Will you sell it to me for such and such, may Allah forgives you?' I said: 'Yes, it is yours. '''(One of the narrators) Abu Nadrah said: "This became a phrase that was used by the Muslims: 'Do such and such, may Allah forgive you.
Sunan an-Nasa'i Book 44, Hadith 193