Sahih Muslim Book 27, Hadith 27
I heard 'Adi b. Hatim say that a person asked that and then narrated (the hadith) like one (mentioned above), but he made this addition:" Here are four hundred (dirhams) for you out of my gift."
You asked me for one hundred dirhams and I am the son of Hatim; by Allah, I will not give you. But then he said: (I would have done that) if I had not heard Allah's Messenger (ﷺ) say: He who takes an oath, but then finds something better than that, should do that which is better.
Abd al-Rahman b. Samura, don't ask for authority for if it is granted to you for asking for it, you would be commissioned for it (without having the support of Allah), but if you are granted it without your asking for it. You would be helped (by Allah) in it. And when you take an oath and find something else better than that, expiate for (breaking) your oath, and do that which is better. This hadith has also been transmitted on the authority of Ibn Farrukh.
The above hadith is narratted through another chain of transmitters.