Sayyiduna Samurah bin Jundub and Sayyiduna Imran bin Husayn (may Allah be pleased with them both) discussed (this matter) with each other. Sayyiduna Samurah (may Allah be pleased with him) related that he had preserved from the Messenger of Allah (peace and blessings be upon him) two pauses (moments of silence): one pause when he (peace and blessings be upon him) said the takbir, and one pause when he (peace and blessings be upon him) finished reciting "not of those who have earned anger, nor of those who go astray" [al-Fatihah: 7]. Sayyiduna Imran (may Allah be pleased with him) disputed this, so they wrote to Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) about it, and his letter to them stated that Samurah had remembered correctly.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 15401