He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him. (John 3:36 KJV)
"What is it to believe on Christ?" It is, to feel your need of him; to believe that he is able and willing to save you, and to save you now; and to cast yourself unreservedly on his mercy, and trust in him alone for your salvation.
J.W. Chickering 1831-1913
Taken from the book A Pastor's Counsel: Wise Words for Weary, Wounded, and Wandering Sheep