7 And I do this for a wise purpose; for thus it whispereth me, according to the workings of the Spirit of the Lord which is in me. And now, I do not know all things; but the Lord knoweth all things which are to come; wherefore, he worketh in me to do according to his will.
8 And my prayer to God is concerning my brethren, that they may once again come to the knowledge of God, yea, the redemption of Christ; that they may once again be a delightsome people.
I love how Mormon describes his process in deciding to include the small plates. First, he begins with a righteous purpose and a desire to do what he can to help his brethren one day come to know God and the redemption of Christ. Then, he goes to work trying to do the best he can at compiling his records. He comes across the small plates and reads them and is deeply impressed by their witness of Christ. Then, he feels a prompting that he does not fully understand to include the plates. And he does not doubt or question that prompting but knows that he is including them for a wise purpose that is known to the Lord.
Mormon here is a great exemplar of how we can and should receive revelation from the Lord.