Forgetting to say ((prayer is better than sleep)) during the adhaan of the Fajr prayer
Question: What is the ruling if the mu.adhdhin forgets to say ((prayer is better than sleep))[during the adhaan of the Fajr prayer)?
Response: The ruling regarding the one who forgot to say ((prayer is better than sleep)) during the adhaan of the Fajr prayer is that it is known to the people of knowledge that his adhaan is correct, because the saying of ((prayer is better than sleep)) during the adhaan of the Fajr prayer is a Sunnah and not obligatory, the evidence being that when `Abdullaah ibn Zayd (radhi-yAllaahu ‘anhu) saw the adhaan in his dream, it did not contain the words ((prayer is better than sleep)) [transmitted by Abu Daawood No.449, Ahmad No.4/43]. Therefore, the saying of these words [((prayer is better than sleep))] is not a condition (for the correctness of the adhaan of the Fajr prayer]; So if a person said it during the adhaan of the Fajr prayer, then that is better, and if he did not, then there is no harm.
Shaykh Ibn ‘Uthaymeen
I`laam al-Mu`aasireen bi-Fataawa Ibn `Uthaymeen – Page 51 source:fatwaonline.com