I think most of us remember with assurance the words of the Charles Wesley hymn which was his own personal testimony: His Spirit answers to the blood, And tells me I am born of God!
Wesley testified here and in many other hymns to an inner illumination! When I became a Christian, no one had to come to me and tell me what Wesley meant. That is why Jesus taught that whosoever is willing to do His will shall have a revelation in his own heart. He shall have an inward revelation that tells him he is a child of God.
Too many persons try to make Jesus Christ a convenience. They reduce Him simply to a Big Friend who will help us when we are in trouble.
That is not biblical Christianity! Jesus Christ is Lord, and when an individual comes in repentance and faith, the truth flashes in. For the first time he finds himself saying, “I will do the will of the Lord, even if I die for it!”