Genesis 8:5

And the waters decreased continually until the tenth month: in the tenth month, on the first day of the month, were the tops of the mountains seen.

Cross-reference

Genesis 7:11 gives the exact start date of the flood, which is the beginning of the timeline that leads to the waters receding here.

Psalm 104:8 poetically describes waters receding from mountains, echoing the scene of mountain tops becoming visible here.