If any one forgets a prayer or oversleeps, he should observe it when he remembers it ; there is no expiation for it except that.
Sunan Abi Dawud Book 2, Hadith 52
← Previous Hadith There is no remissness in sleep, it is only when one is awake that there is remissness when you delay saying the prayer till the time for the next prayer comes.

Sunan Abi Dawud Book 2, Hadith 51 Next Hadith → The Messenger of Allah (ﷺ) was on his journey. They (the people) slept abandoning the Fajr prayer. They awoke by the heat of the sun. Then they travelled a little until the sun rose high. He (the Prophet) commanded the mu'adhdhin (one who called for prayer) to call for prayer. He then offered two rak'ahs of prayer (sunnah prayer) before the (obligatory) fajr prayer. Then he (the mu'adhdhin) announced for saying the prayer in congregation (i.e. he uttered iqamah). Then he led them in the morning prayer.

Sunan Abi Dawud Book 2, Hadith 53