In Genesis, Noah was told to coat the Ark’s inside and outside with pitch.
Genesis 6:14 instructs Noah to cover the vessel with pitch inside and out. Pitch is a thick, waterproofing substance made from natural bitumen, tar, or resinous materials, depending on the historical context and translation.
The instruction has a practical purpose within the story: a large wooden vessel exposed to continuous water would need its seams and surfaces sealed. The Hebrew term is related to covering or atonement, and translators commonly render it as pitch or bitumen.
Pitch is sometimes confused with the Ark’s building material. Genesis names gopher wood for construction and pitch for waterproofing. They are separate elements in the description, just as the rooms, decks, door, and upper opening are separate construction details.