Genesis 6:15

This is how you shall make it: the length of the ark three hundred cubits, its breadth fifty cubits, and its height thirty cubits.

Genesis 7:20

The water prevailed fifteen cubits higher, and the mountains were covered.

Deuteronomy 3:11

(For only Og king of Bashan was left of the remnant of the Rephaim. Behold, his bedstead was an iron bedstead; it is in Rabbah of the sons of Ammon. Its length was nine cubits and its width four cubits by ordinary cubit.)

Treasury of Scripture Knowledge

Summary

And this is the fashion which thou shalt make it of: The length of the ark shall be three hundred cubits, the breadth of it fifty cubits, and the height of it thirty cubits.

Bible References

Cubits

Genesis 7:20
The water prevailed fifteen cubits higher, and the mountains were covered.
Deuteronomy 3:11
(For only Og king of Bashan was left of the remnant of the Rephaim. Behold, his bedstead was an iron bedstead; it is in Rabbah of the sons of Ammon. Its length was nine cubits and its width four cubits by ordinary cubit.)