When any one of you omits the prayer due to sleep or he forgets it, he should observe it when he remembers it, for Allah has said:" Observe prayer for remembrance of Me."
Sahih Muslim Book 5, Hadith 402
← Previous Hadith He who forgets the prayer, or he slept (and it was omitted), its expiation is (only) that he should observe it when he remembers it.

Sahih Muslim Book 5, Hadith 401 Next Hadith → The prayer was prescribed as two rak'ahs, two rak'ahs both in journey and at the place of residence. The prayer while travelling remained as it was (originally prescribed), but an addition was made in the prayer (observed) at the place of residence.

Sahih Muslim Book 6, Hadith 1