Charles Ellicott Commentary Exodus 29:12

"And thou shalt take of the blood of the bullock, and put it upon the horns of the altar with thy finger; and thou shalt pour out all the blood at the base of the altar." — Exodus 29:12 (ASV)

You shall take of the blood ... and put it upon the horns of the altar. — It has been already noticed that the virtue of the altar was considered to reside especially in its horns; hence fugitives clung to them (1 Kings 1:50; 1 Kings 2:28).

In all sin offerings it was required:

1. That some of the victim’s blood should be smeared upon the altar’s horns; and
2. That the remainder should be poured at its base (Leviticus 4:7; Leviticus 4:18; Leviticus 4:30; Leviticus 4:34).