(See this introduction to the idea of "Sister Scriptures".)
Doctrine and Covenants 68:6
6 Wherefore, be of good cheer, and do not fear, for I the Lord am with you, and will stand by you; and ye shall bear record of me, even Jesus Christ, that I am the Son of the living God, that I was, that I am, and that I am to come.
Acts 23:11
11 And the night following the Lord stood by him, and said, Be of good cheer, Paul: for as thou hast testified of me in Jerusalem, so must thou bear witness also at Rome.
Mosiah 2:41
41 And moreover, I would desire that ye should consider on the blessed and happy state of those that keep the commandments of God. For behold, they are blessed in all things, both temporal and spiritual; and if they hold out faithful to the end they are received into heaven, that thereby they may dwell with God in a state of never-ending happiness. O remember, remember that these things are true; for the Lord God hath spoken it.
4 Nephi 1:18
18 And how blessed were they! For the Lord did bless them in all their doings; yea, even they were blessed and prospered until an hundred and ten years had passed away; and the first generation from Christ had passed away, and there was no contention in all the land.