Leviticus 4:7

(7) And the priest shall put.—That is, the high priest. With the finger thus dipped into it, he is to put some of the blood on each of the four horns of the golden altar on which the incense was offered.

This process, too, was peculiar to the sacrifice of the sin offering. The altar was placed in the holy place before the vail which separated off the holy of holies (Exodus 30:1-6). According to the practice which obtained in the time of Christ, the priest began by putting the blood first on the north-east horn, then on the north-west, then on the south-west, and, lastly, on the south-east horn. He dipped his finger in the blood of the bowl at the sprinkling of each horn, and wiped his finger on the edge of the bowl between the separate sprinklings, as the blood which remained on his finger from one horn was not deemed fit to be put on the other.

And shall pour all the blood.—That is, all the remaining blood. The bulk of the blood which remained, after expending the small quantity on the horns of the incense altar inside the sanctuary, the priest poured out at the bottom of the altar of burnt offering, which stood outside the holy place. At the time of the second Temple, there were at the southwest horn of this altar two holes, like two nostrils, through which the blood ran into a drain conveying it into the brook of Kedron.