Genesis 8:11

and the dove came in to him in the evening; and, lo, in her mouth was an olive leaf, plucked off. So Noah knew that the waters were abated from off the earth. Noah continued to give evidence of the patience of faith by once more waiting a full week before he sent out another dove. This dove made a wide flight in search of the plains and did not return until the evening. But the token which she brought was a fair sign of deliverance soon to be expected, for in her bill she carried a leaf, or small twig, of an olive-tree, a species which is found only in the lowlands, has green leaves throughout the year, and is able to endure the action of water for a long time. Thus Noah had proof that the waters had fallen to the level of the olive-trees in the valleys.