Doubt is not a sign of weakness, but rather an opportunity to remind ourselves of what and why we believe as we do. John, the greatest prophet of God according to Jesus, had the privilege to baptize Jesus, and to have His identity confirmed by the Holy Spirit and the voice of God, Himself (Mk. 1:9-11; Lk. 7:28). Even John had one of those days when began to question whether or not Jesus was really the Messiah. Perhaps he thought, "If Jesus is really the Messiah, why am I in prison?" In Luke 7:17-28, John sends his disciples to ask Jesus to verify that He is the Christ. He told them to observe the miracles and to go and tell John. He did not rebuke John, nor did He remind him of His baptism; He gave John more evidence of His identity to strengthen his faith. He was preparing him for the trial he would soon face (Mt. 14:12).
Looking back on past events in order to keep one's faith alive, is very Scriptural! The Word has several examples of the times when the Lord told men to view something as a reminder of His work on their behalf. Here are just a few examples. He told Noah that the rainbow was a sign of promise (Gen. 9:15-16). He told the people of Israel to remember how He led them for forty years through the wilderness by a pillar of cloud by day, and a pillar of fire by night (Deut. 8:2; Ex. 13:21). And, He inspired Joshua to have the children of Israel create a pile of stones, taken out of the dry Jordon, to be a remembrance of their entering the land of promise (Josh. 4:1-24).
Christians also have something Jesus left us to remind us of God's amazing love and sacrifice. In 1 Corinthians 11:23-26, Paul writes, "For I have received of the Lord that which also I delivered unto you, That the Lord Jesus the same night in which He was betrayed took bread: and when He had given thanks, He brake it, and said, Take, eat: this is my body, which is broken for you: this do in remembrance of Me. After the same manner also He took the cup, when He had supped, saying, This cup is the new testament in My blood: this do ye, as oft as ye drink it, in remembrance of Me. For as often as ye eat this bread, and drink this cup, ye do shew the Lord's death till He come."
The Lord's Supper is a reminder that He came, and He is coming again!