Sayyiduna Abu Hurayrah (may Allah be pleased with him) said: I saw Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) prostrate in Surah al-Najm during the Fajr prayer, and then he began another surah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3762