Read Genesis 17:17
Then Abraham fell on his face and laughed, and said in his heart, "Shall a child be born to a man who is one hundred years old? And shall Sarah, who is ninety years old, bear a child?"
When John Paton was translating the Bible for a South Pacific island tribe, he discovered that they had no word for trust or faith. One day a native who had been running hard came into the missionary's house, flopped down in a large chair and said, "It's good to rest my whole weight on this chair." "That's it!" exclaimed Paton. "I'll translate faith as resting one's whole weight on God."
Abraham was a man of faith--but sometimes that faith was in the wrong place. When God told him he would have a son, he looked at himself and said, "Shall a child be born to a man who is one hundred years old?" Obviously, from a human perspective that was a ridiculous notion. Instead of resting his faith wholly upon God, Abraham was trying to carry part of the burden himself.
Faith always falters when we trust in our own capabilities. If something was doable by human standards, faith would not be necessary. The essence of faith requires that it is something that can be accomplished only if God undertakes it for us. The ultimate example of this, of course, is our own salvation. When He was asked, "Who then can be saved?" Jesus responded, "The things which are impossible with men are possible with God" (Luke 18:27). The apostle Paul declares in Philippians 4:13, "I can do all things," but then he goes on to clarify, "through Christ who strengthens me." It is not we who can do all things, but Christ.
Where is your faith resting? Are you depending upon your own resources, or are you resting your whole weight upon God? Whether it's for your ultimate salvation or some daily responsibility, have faith in God. Only He can do the impossible.
What the world calls ridiculous, God calls faith.