Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates about Sayyiduna Umar (may Allah be pleased with him): He said to his muezzin that when you reach "Hayya 'ala as-Salah" in the Fajr adhan, then say: "As-salatu khayrun min an-nawm, as-salatu khayrun min an-nawm."