People will be questioned the most about the mastership of the Ahle Bait (peace be on them)

عَنْ اَبِي حَمْزَةَ عَنْ اَبِي جَعْفَرٍ ؑ قَالَ بُنِيَ الْاِسْلَامُ عَلَى خَمْسٍ عَلَى الصَّلَاةِ وَ الزَّكَاةِ وَ الصَّوْمِ وَ الْحَجِّ وَ الْوَلَايَةِ وَ لَمْ يُنَادَ بِشَيْ‏ءٍ كَمَا نُودِيَ بِالْوَلَايَةِ

Abu Hamzah (al-Thumaali) reports from Imam Abu Ja’far (al-Baqer – peace be on him) said,

“Islam is built on five (pillars): On prayers, poor-rate, fasting, Hajj and mastership (of Ahle Bait – peace be on them). Nothing will be called out as mastership will be called out.”

Note

This explanation flows without breaks. The Messenger and Imams have knowledge.

Reference

1. Al-Kaafi, vol. 2, p. 18, H. 1, 3, 7 and 8 (with minor variations)
2. Al-Amaali of al-Shaikh al-Saduq (r.a.), p. 268, Majlis 45, H. 14
3. Al-Amaali of al-Shaikh al-Toosi (r.a.), p. 124, Majlis 5, H. 192