Sayyiduna Abu Mahdhurah (may Allah be pleased with him) says: I was a young boy, and I gave the adhan before the Prophet (peace and blessings be upon him) on the day of Hunayn. When I reached "Hayya 'ala al-salah, hayya 'ala al-falah," the Prophet (peace and blessings be upon him) said to me: "Add this to it as well: Al-salatu khayrun min al-nawm (Prayer is better than sleep)."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6709