Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Prophet Muhammad (peace and blessings be upon him) said: "Whoever catches one rak'ah of the Asr prayer before the sun sets has caught that (prayer), and whoever catches one rak'ah of the Fajr prayer before the sun rises and performs one rak'ah after the sun has risen, he has caught that (Fajr prayer)."