What is the ruling on one who doubts a pillar of prayer and does not pay attention to his doubts, then becomes certain later, but does not know the number or type of prayers in which he doubted, and is there a difference of opinion among scholars on this matter?

If the doubt arises from waswasa (whispers of Satan/obsessive thoughts), one must ignore it and pay no attention to it, and there is no need to repeat the prayers. A person afflicted with waswasa should not heed their doubt, and doubt after completing an act of worship has no effect.

However, if the doubt does not stem from waswasa, and the worshipper doubts having omitted a pillar (rukn), they must perform the doubted part and what follows it; otherwise, repeating the prayer becomes obligatory. If the worshipper becomes certain after the prayer that they omitted a pillar, they must perform a rak'ah in place of the rak'ah from which the pillar was missing, as long as the interval is not long. If the interval is long, repeating the prayer becomes obligatory.

If this occurs in several prayers and the worshipper doubts which specific prayer it was, they must make up what will ensure certainty of their acquittal. However, if the worshipper becomes certain after the prayer that they did perform the doubted pillar, then nothing is required of them, and their prayer is valid. If the worshipper concludes their prayer while doubting its completeness, then becomes certain it was complete, they are required to repeat it; this is the more apparent (stronger) opinion.