Is it legislated to say "Allahu Akbar" after the prayer, or is it sufficient to say "Astaghfirullah" three times, and is saying "Allahu Akbar" aloud after the prayer a confirmed Sunnah?

Scholars have differed regarding the audibility of dhikr (remembrance of Allah) and takbir (proclaiming Allah's greatness) after prayer: The majority opinion is that it is not recommended, and Imam Shafi'i interpreted the hadiths that suggest audibility as being for teaching purposes, not for continuous practice. However, a group, including Al-Tabari, Ibn Hazm, and Ibn Taymiyyah, held the view that it is recommended. The matter in this regard is flexible.

Scholars also differed on the meaning of "takbir" mentioned in the hadith of Ibn Abbas (may Allah be pleased with them both): 1. Some said it refers to repeating "Allahu Akbar" three consecutive times. 2. Others said it refers to saying "Subhan Allah (Glory be to Allah), Al-hamdulillah (All praise is due to Allah), and Allahu Akbar (Allah is the Greatest)" thirty-three times after the prayer, combining the various narrations. The Prophet (peace and blessings be upon him) would begin with seeking forgiveness after prayer, then say: "O Allah, You are As-Salam (the Source of Peace), and from You is all peace. Blessed are You, O Possessor of Majesty and Honor," and then follow with the rest of the remembrances.