Leviticus 6:11
And he shall put off his garments, and put on other garments, and carry forth the ashes without the camp unto a clean place.
Cross-reference
Leviticus 4:12 also requires taking a sin offering bull outside the camp to a clean place — the same procedure as for the ashes.
Leviticus 4:21 repeats the same command for the assembly's sin offering — carry the bull outside the camp.
In Leviticus 16:23, Aaron removes his linen garments after the atonement ritual — same action of taking off priestly garments as here.
In Leviticus 16:24, Aaron washes and puts on other garments after ministering — parallel to the priest changing clothes to carry ashes out here.
Leviticus 16:27 also has sin offerings carried outside the camp and burned — a parallel disposal ritual.
Leviticus 1:16 describes placing bird ashes beside the altar — the same ashes later carried outside in 6:11.
In Ezekiel 44:19, priests change garments after ministry to avoid sanctifying the people — similar to the change of clothes for ash removal here.
Hebrews 13:11-13 uses the 'outside the camp' pattern as a type of Christ's suffering outside the gate.