For I gave them the words you gave me, and they accepted them. They knew with certainty that I came from you, and they believed that you sent me.

John 17:8

This is the bed-rock of belief!  Jesus, the sent one, is sent by his Father.  This is the sovereign work of the Father, and the Father asks us to believe who Jesus is.  That makes all the difference.  Jesus said that disciples knew that God sent Jesus, His Son.  That is the most important aspect of belief.  All else is built on that, who Jesus is!

This is what God revealed to the disciples.  Jesus was certain that they believed in God and Jesus Christ.  He was satisfied.  He is about to be beaten and crucified on a Roman cross.  It is hard to believe that God wanted that.  But we know that our Salvation is rooted in that fact.

Soul, rest.  Do not try to figure this out by human reason.  It is revealed to us!  Believe it and everything falls into place.