Genesis 8:20

builded an altar unto the Lord It will be noticed that, in this account by J, the first thing that Noah does, on leaving the ark, is to build an altar, and to offer sacrifice. In J's estimation sacrifice was primitive, and not merely Mosaic, in origin. See note on Genesis 7:2.

In P there is no mention of "altar" or "sacrifice" before the institution of the Levitical system in the wilderness.

of every clean beast, and of every clean fowl The clean animals were used for sacrifice. Cf. Genesis 7:2. Observe the mention of "clean fowl" implying the distinction between clean and unclean fowl. This distinction was not observed in Genesis 7:3; Genesis 7:8. The number of "clean" animals, seven pairs of each, in the ark, according to J, would allow for the offering of sacrifice.

In the Babylonian account, also, sacrifices were at once offered to the gods on quitting the ark.

and offered burnt offerings The word for "burnt offering" is -ôlâh, which is derived from a verb meaning "to go up." A burnt-offering, or -ôlâh, was the sacrifice which "went up" to God, being different from other sacrifices, because the whole of it was consumed in the fire of the altar. The offerer of an -ôlâhate nothing of the sacrifice; nor did the priest. It was in an especial sense a propitiatory offering: compare David's offering in 2 Samuel 24:25. The -ôlâhis different from the minḥahof Genesis 4:3. LXX renders εἰς ὁλοκάρπωσιν, Lat. holocausta.