Genesis 8:6

And it came to pass at the end of forty days, that Noah opened the window of the ark which he had made:

At the end of forty days. He waited forty days, after the decrease of the waters, corresponding to the forty days during which the waters had increased. It is easy to imagine the ardent longing Noah and his family must have felt to enjoy again the sight of land, as well as breathe the fresh air; and it was perfectly consistent with faith and patience to make enquiries whether the earth was yet ready.

Opened the window - [Hebrew, chalown (H2474), a different word from that used in Genesis 6:16, and as it elsewhere denotes a narrow opening for the light (cf. Joshua 2:15; Joshua 2:18; Joshua 2:21; 1 Kings 6:14; Ezekiel 40:16; Ezekiel 41:16; Ezekiel 41:26), it was probably a small division or portion of the sky-light, that extended upon the roof along the whole length of the ark.]