(a) It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that in the first adhan, after 'Hayya 'ala al-falah', there was: 'Al-salatu khayrun min al-nawm, al-salatu khayrun min al-nawm' (Prayer is better than sleep, prayer is better than sleep).
(b) It is narrated from Ibn Umar (may Allah be pleased with them both) that 'Hayya 'ala al-falah, hayya 'ala al-falah, al-salatu khayrun min al-nawm' (Come to success, come to success, prayer is better than sleep) was said twice in the first adhan, that is, in the morning adhan.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 1986