The Messenger of Allah (ﷺ) said: Ali, do not instruct the imam during the prayer.

Abu Dawud said: The narrator Abu Ishaq heard only for traditions from al-Harith, this tradition is not one of them.
Sunan Abi Dawud Book 2, Hadith 519
← Previous Hadith The Prophet (ﷺ) prayed and recited the Qur’an in it. He was then confused in it (in his recitation). When he finished (his prayer), he said to Ubayy (b. Ka’b): Did you pray along with us? He said: Yes. He said: What prevented you (from correcting me)?

Sunan Abi Dawud Book 2, Hadith 518 Next Hadith → The Prophet (ﷺ) said: Allah, the Most High, continues to turn favourably towards a servant while he is engaged in prayer as long as he does not look to the side (by turning the neck), but if he does so, He turns away from him.

Sunan Abi Dawud Book 2, Hadith 520