A.A. Bonar in his “Exposition of Leviticus” says about Leviticus 5 that:
“..the trespass offering was offered in cases where the sin was more private and confined to the individual’s knowledge. The sin was known only to the man himself, and so it was less hurtful in its effects…..The trespass-offering was always a ram, It was thus fitted to remind Israel of Abraham’s offering Isaac, when the ram was substituted. The blood of it was always put ‘on the sides’ of the altar; not on the horns, as in the case of the sin-offering, where the offering was of a public nature, and needed to be held up to all.” [pg 43].
However, “The sin-offering being of a more public notice was on that account more fitted to be th usual type of Christ’s offering. It was both public and definite.” [pg 43]