All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
As regards the verses where Allaah explained the six pillars of faith, Allaah Says (what means):
Allaah the Exalted stated the five pillars in the first verse:
1. Belief in Allaah The Almighty.
2. Belief in The Last Day.
3. Belief in angels.
4. Belief in The Books.
5. Belief in the Prophets.
In the second verse Allaah The Almighty stated the sixth pillar: which is the belief in Predestination and Decree.
Allaah described those who do not believe in these pillars as disbelievers and non-Muslims. Allaah Says (what means): {And whoever disbelieves in Allaah, His angels, His books, His messengers, and the Last Day has certainly gone far astray}[Quran 4:136]
Since a person who does not believe in these pillars is described as a disbeliever, then this means that believing in them is obligatory.
May Allaah increase your zeal in knowing your religion!