Belief = Trust
"Let not your hearts be troubled. Believe in God; believe also in me."
According to the ESV Study Bible: "believe" means/denotes "personal, relational trust."
Our belief in God demands that we trust Him. If we don't trust in Him then how can we say we believe in God? What are we believing in if not the fact that the creator and keeper of all things is trustworthy?
"Believe in God" here is translated as imperative command. We are commanded to believe and therefore trust in God.