It is narrated from Azraq bin Qays: I prayed behind Ibn al-Zubayr (may Allah be pleased with them both). He would recite 'Bismillahir-Rahmanir-Rahim' (In the name of Allah, the Most Gracious, the Most Merciful), and then, when he recited "nor of those who have gone astray" [Surah al-Fatihah: 7], he would again recite 'Bismillahir-Rahmanir-Rahim'.
This has been narrated to us from Abu Hurayrah (may Allah be pleased with him) and several other Companions (may Allah be pleased with them).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3059