What is the ruling on praying behind an imam who does not pronounce the hamzat al-qat' (قطع) in "Assalamu Alaikum" and "Allahu Akbar," or who overemphasizes the "seen" (س) in "Assalamu Alaikum"? And is it obligatory to repeat the prayer?

The taslim (salutation) is a pillar of prayer according to the majority of scholars, and its sufficient form is: "Al-salamu alaykum." The Hanafis permitted "salamun alaykum" with a degree of dislike (karahah).

The transition takbirs (saying "Allahu Akbar" when moving between prayer postures) are a sunnah according to the majority of scholars, and obligatory according to the Hanbalis. Their form is "Allahu Akbar," with the hamza of "Akbar" being pronounced with a fatḥa (a-sound); if it is pronounced with a kasra (i-sound) or between a fatḥa and a kasra, and this changes the meaning, the prayer is invalidated. However, if the meaning does not change, it is not invalidated.

It is obligatory for a Muslim to learn correct pronunciation. If one is unable to do so despite exerting effort, they are excused, and their prayer is valid.

It is advisable to admonish an Imam who makes mistakes. If he knows of his mistake and does not correct it, his prayer and his imamate (leading of prayer) are invalid. However, if he is unable to correct it, his prayer is valid, and the prayer of those following him is also valid.

One must be cautious of falling into obsessive doubts (waswasah) and blameworthy strictness. Satan may beautify for the worshipper the idea that the Imam does not properly recite Al-Fatiha, the takbir, or the taslim, and this could lead to dispute and division among worshippers.