Scientists in Germany have studied the way we laugh. They distinguish between social laughs and tickling laughs. Social laughs send out various messages like humor, joy, or satisfaction, but also messages that taunt or mock. Some laughs are audible; some are silent. Long ago, Sarah, the wife of Abraham saw her laugh of unbelief turn to joy. We read in Genesis Chapter 18:12 that when God told Abraham Sarah would give birth to a son at age 90, she laughed silently in unbelief. Her unbelief prompted God to ask, “Is anything too hard for the LORD? God wanted her to know that when He makes a promise, nothing in heaven or hell can prevent Him from doing what He promises. God caused her dead womb to give birth to a son. After she gave birth to Isaac a year later, she laughed differently. In Genesis 21:6, we find her saying this: “God has brought me laughter! All who hear about this will laugh with me. For who would have dreamed that I would ever have a baby? Yet I have given Abraham a son in his old age!” Faith is simply relying on what God has promised. The Apostle Paul said of Abraham (Romans 4:21): “He was absolutely convinced that God was able to do anything he promised.” Our faith is on solid ground when we discover what God has promised us in His word and we rest in them.