Multiple commentators (Calvin, Gill, Barnes) highlight that Aaron, as a sinner himself, first had to offer a sacrifice for his own sins before he could atone for the people. They explain this demonstrates the 'weakness' of the Old Testament priesthood and serves as a powerful illustration of why a better High Priest was needed—Jesus Christ, who was sinless and did not need to make atonement for Himself (Hebrews 7:27–28).