From the LCMS website:
Noah, the son of Lamech (Gen 5:30), was instructed by God to build an ark, in which his family would find security from the destructive waters of a devastating flood that God warned would come. Noah built the ark, and the rains descended. The entire earth was flooded destroying “every living thing that was on the face of the ground, both man and beast” (7:23). After the flood waters subsided, the ark came to rest on the mountains of Ararat. When Noah determined it was safe, and God confirmed it, he and his family and all the animals disembarked. Then Noah built an altar and offered a sacrifice of thanksgiving to God for having saved his family from destruction. A rainbow in the sky was declared by God to be a sign of His promise that never again would a similar flood destroy the entire earth (8;20). Noah is remembered and honored for his obedience, believing that God would do what He said He would.