What are the rulings concerning the takbirat (saying "Allahu Akbar") in prayer? Is merely moving the lips sufficient for them? When should the takbir be uttered during transitions? Should one look at the index finger when moving it during the tashahhud? And is a person sinful if they observe errors in the prayers of others in the mosque?

The takbirat al-ihram (opening takbir) is one of the pillars of prayer, while the rest of the takbirs are either obligations or recommendations. The minimum sufficient for the takbir is to move the tongue with it and pronounce it, and it is better to make oneself hear it to avoid scholarly differences. It is recommended for the Imam to pronounce the takbir aloud, and for the congregant (ma'mum) and the individual praying alone to say it silently. The takbirs should accompany the movement of transition. The Sunnah in the tashahhud is to look at the index finger as a recommendation. Whoever catches the Imam bowing must perform the takbirat al-ihram while standing, then bow without the need for a takbir for bowing. There is no sin on a person for another's mistake. The prescribed action is to advise the one who erred gently and kindly, and advice is an obligation, either individually incumbent (wajib 'ayni) or communally incumbent (wajib kifa'i).