What must a person believe in order to be saved?
A person must believe the Gospel with all the heart: that He died, was buried, and rose from the dead. Believing this as God's promise, not doubting or merely hoping, one rests on it, and God declares, 'thou shalt be saved.'
Les teaches from Romans 10 that these are verses every servant of God uses when dealing with someone in salvation. The Gospel is that He died, was buried, and rose from the dead. If you believe that with all your heart, thou shalt be saved—not if, maybe, or hope so. When we believe God promised it as a fact, thou shalt be saved. That is a promise, and God expects us to rest on His promises, not doubt or wonder. Because He said it, we can believe it. Romans 10 goes on: with the heart, not with the head.