It is narrated from Sayyiduna Samurah bin Jundub (may Allah be pleased with him) that there were two pauses in the prayer of the Messenger of Allah (peace and blessings be upon him). Sayyiduna Imran bin Husayn (may Allah be pleased with him) said: I have not preserved two (pauses) from the Messenger of Allah (peace and blessings be upon him). They wrote about this matter in a letter to Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him), and Ubayy bin Ka'b (may Allah be pleased with him) wrote that Samurah (may Allah be pleased with him) had remembered correctly. We asked Qatadah (may Allah have mercy on him): What are those pauses? He said: One pause when he says the takbir and begins the prayer, and the other at the time of ruku', after finishing the recitation. Then he said: The other (time): at the opening takbir, and one pause after "Not of those who have earned (Your) anger, nor of those who go astray" [Surah al-Fatihah: 7].
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3079