Genesis 6:14

I will destroy them with the earth, but make thee an ark — I will take care to preserve thee alive. This ark was like the hulk of a ship, fitted not to sail upon the waters, but to float waiting for their fall. God could have secured Noah, by the ministration of angels without putting him to any care or pains, but he chose to employ him in making that which was to be the means of his preservation, both for the trial of his faith and obedience, and to teach us that none shall be saved by Christ, but those only that work out their salvation; we cannot do it without God, and he will not without us: both the providence of God and the grace of God crown the endeavours of the obedient and diligent. God gave him particular instructions concerning this building. It must be made of Gopher — wood; Noah, doubtless, knew what sort of wood that was, though now we do not. He must make it three stories high within: and, He must divide it into cabins with partitions, places fitted for the several sorts of creatures, so as to lose no room. Exact dimensions are given him, that he might make it proportionable, and might have room enough in it to answer the intention, and no more. He must pitch it within and without: without, to shed off the rain, and to prevent the water from soaking in; within, to take away the ill smell of the beasts when kept close. He must make a little window towards the top to let in light. He must make a door in the side of it by which to go in and out.