Noah sent forth a raven Through the window of the ark; which went forth As the Hebrew phrase is, going forth and returning; that is, flying about, but returning to the ark for rest; probably not in it, but upon it. This gave Noah little satisfaction: therefore, he sent forth a dove Which returned the first time with no good news, but probably wet and dirty; but the second time she brought an olive-leaf in her bill, which appeared to be fresh plucked off; a plain indication that now the trees began to appear above water. Note here, that Noah sent forth the dove a second time, seven days after the first time, and the third time was after seven days too: and probably the first sending of her out was seven days after the sending forth of the raven. The olive-branch is an emblem of peace.
Genesis 8:7-12
7 And he sent forth a raven, which went forth toc and fro, until the waters were dried up from off the earth.
8 Also he sent forth a dove from him, to see if the waters were abated from off the face of the ground;
9 But the dove found no rest for the sole of her foot, and she returned unto him into the ark, for the waters were on the face of the whole earth: then he put forth his hand, and took her, and pulled her in unto him into the ark.
10 And he stayed yet other seven days; and again he sent forth the dove out of the ark;
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.
12 And he stayed yet other seven days; and sent forth the dove; which returned not again unto him any more.