The Messenger of Allah (peace and blessings be upon him) would seek forgiveness three times for the front row and once for the second

Sayyiduna al-Irbad bin Sariyah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) used to seek forgiveness for the first row three times and for the second row once.
This hadith has a sahih (authentic) chain, and the two Shaykhs used as evidence such narrations of Tabi'in who are the only ones to narrate them.

Sayyiduna Abdullah bin al-Zubayr (may Allah be pleased with them both) said to the people from the pulpit: When any one of you enters the mosque while the people are in bowing (ruku'), he should bow as soon as he enters and then walk in the state of bowing until he joins the row, for this is the Sunnah.
This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it.

Qays bin Ubad narrates: I was standing in prayer in the first row in the mosque at Madinah when a man pulled me from behind, moved me aside and stood in my place himself. When he finished the prayer, it turned out that he was Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him). He said: O young man, may Allah not grieve you; this was the instruction of the Messenger of Allah (peace and blessings be upon him) to us, that we (the people of knowledge) should stay close to him. Then he faced the qiblah and said three times: By the Lord of the Ka'bah, the people of authority and management (the rulers) have perished! I do not grieve for them; rather, I grieve for those whom they have led astray.
This hadith is sahih (authentic) on the condition of Imam Bukhari, but they did not record it; Yusuf bin Ya'qub al-Sadusi is a trustworthy narrator of Bukhari.

Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "When the imam says 'Allahu akbar' (Allah is the Greatest), then you say 'Allahu akbar'; and when he says 'Sami' Allahu liman hamidah' (Allah hears the one who praises Him), then you say 'Rabbana wa lakal-hamd' (Our Lord, and to You belongs all praise)."
This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it with these words. It contains an important Sunnah: that the follower should wait until the imam completes the takbir and should not say the takbir together with him (at the same moment).

Sayyiduna Samurah bin Jundub and Sayyiduna Imran bin Husayn (may Allah be pleased with them both) held a scholarly discussion, and Samurah bin Jundub related that he had preserved from the Messenger of Allah (peace and blessings be upon him) two pauses (periods of silence): one pause when he said the (opening) takbir, and another pause when he completed his recitation before going into bowing.
This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it with these words. Hasan al-Basri's hearing from Samurah is established, so this narration is connected.

Sayyiduna Abu Hurayrah (may Allah be pleased with him) came to the mosque of Banu Zurayq and said: There are three things that the Messenger of Allah (peace and blessings be upon him) used to do but people have abandoned them: (first) he would raise his hands in prayer such that they went above his ears, and (second) after the recitation he would remain silent for a short while in order to ask Allah for His bounty.
This is a supporting report for the previous hadith, and its chain is sahih (authentic).