Midrash sur Berakhot 1:13

The dwelling of the moon is between cloud and thick darkness made like two dishes turned one over the other, and when it is the conjunction of the moon these two clouds turn in the east quarter and (the moon) goes forth from between them like a ram's horn. On the first night (is revealed) one measure (of light), on the second night the second measure, and so on until the half of the month when the moon is fully revealed, and from the middle of the month these two clouds turn their faces in the west quarter. The corner (i.e. crescent) of the moon with which it comes forth first, (the same) begins to enter and is covered therein by the two (clouds) on the first night (by) one measure, on the second night (by) a second measure, and so on to the end of the month until || it is entirely covered. And whence do we know that it is placed between two clouds? Because it is said, "When I made the cloud the garment thereof, and thick darkness a swaddlingband for it" (Job 38:9). And whence do we know that it becomes entirely covered? Because it is said, "Blow ye the trumpet in the new moon, at the covering, on our solemn feast day" (Ps. 81:8). "At the covering," on the day when it is entirely covered, blow ye the trumpet in the new moon.