Here's the relevant passage from Genesis 8:8-12:
> 8 Then he sent out a dove from him, to see if the waters had receded from the face of the ground. 9 But the dove found no place to set its foot, and it returned to him to the ark, for the waters were still on the face of all the earth. So he put out his hand and took it into the ark. 10 He waited another seven days, and again he sent out the dove from the ark. 11 And the dove came back to him in the evening, and behold, in its beak was a freshly plucked olive leaf. So Noah knew that the waters had receded from the earth. 12 He waited another seven days, and sent out the dove, and it did not return to him anymore.
This story is symbolic and has been interpreted in many ways.