Aaron

Hebrews 9:7, 12, 24, 25
But only the high priest entered the inner room, and then only once a year, and never without blood, which he offered for himself and for the sins the people had committed in ignorance. . . .

a young

Leviticus 4:3
If the anointed priest sins, bringing guilt on the people, he must bring to the LORD a young bull without blemish as a sin offering for the sin he has committed.

Leviticus 8:14
Moses then brought the bull near for the sin offering, and Aaron and his sons laid their hands on its head.

Numbers 29:7-11
On the tenth day of this seventh month, you are to hold a sacred assembly, and you shall humble yourselves; you must not do any work. . . .

a ram for a burnt-offering

Leviticus 1:3, 10
If one's offering is a burnt offering from the herd, he is to offer an unblemished male. He must bring it to the entrance of the Tent of Meeting for its acceptance before the LORD. . . .

Leviticus 8:18
Then Moses presented the ram for the burnt offering, and Aaron and his sons laid their hands on its head.

Leviticus 9:3
Then speak to the Israelites and say, 'Take a male goat for a sin offering, a calf and a lamb, both a year old and without blemish, for a burnt offering,