Genesis 8:11
And the dove came in to him in the evening; and, lo, in her mouth was an olive leaf pluckt off: so Noah knew that the waters were abated from off the earth. And the dove came in to him in the evening; and, lo, in her mouth was an olive leaf pluckt off: so Noah knew that the waters were abated from off the earth.
Forty days after the mountaintops appeared the raven was sent out, and the dove of the verse followed after that sending. The raven flew to and fro without bringing back the information sought, and the first dove found no rest or footing and returned, so the dove in the verse was sent a second time seven days later. Its return in the evening with a freshly plucked olive leaf in its mouth gave Noah evidence and knowledge that the floodwaters had abated and receded and decreased and that the earth was becoming dry.
Noah and his family of eight had been shut up so long in the ark and were anxiously watching for the decrease and longing to go out upon the earth again, so the leaf brought them great rejoicing as proof the water was down. Even with this sign of decreasing water, they remained patiently inside the ark waiting for God's special direction to depart.
The flood to which the verse belongs came as divine judgment because human sin and iniquity brought destruction upon the world. God provided the ark, a massive boat, to save all who would hear the warning, turn from unrighteousness and believe the truth Noah preached, by which all were tested, yet only eight persons were saved. The sins that brought those judgments are increasing again and punishment for them remains certain.