“And he shall sprinkle of the blood on it with his finger seven times, and cleanse it, and hallow it from the uncleannesses of the children of Israel.”
Then the blood of both sacrifices will be sprinkled on the altar with the High Priest's finger ‘seven times' in order to indicate complete cleansing. The purpose is in order to ‘make it holy', re-separating it off to God from all uncleanness, by removing all traces of the uncleannesses of the children of Israel (compare Leviticus 4:6-7; Leviticus 8:11).