Charles Ellicott Commentary Leviticus 1:9

"but its inwards and its legs shall he wash with water: and the priest shall burn the whole on the altar, for a burnt-offering, an offering made by fire, of a sweet savor unto Jehovah." — Leviticus 1:9 (ASV)

But his inwards. —However, before the cut-up victim was arranged in this way to be burned, the stomach, the intestines, and the feet had to be thoroughly cleansed. In the time of the Second Temple, this washing had to be repeated three times before the ablution was considered complete.

And the priest shall burn. —The word used here is not the one generally used to denote consuming by fire, but it originally signifies to make a fume or vapour by incense. It is used in connection with all sacrifices (Leviticus 2:2; Leviticus 2:9; Leviticus 3:5; Leviticus 3:11; Leviticus 4:10; Leviticus 4:19; Leviticus 6:8; Leviticus 7:5, and so on), and the idea intended to be conveyed by this is that people on earth suitably brought their gift to God in heaven by causing the odour emitted from the burning sacrifice to ascend as a sweet-smelling savour to heaven.