Peri (G4012) is a preposition meaning about, concerning, or around. It appears over 330 times in the NT and governs a wide range of meanings: proximity (around), reference (concerning), or representation (on behalf of in some constructions).
The 'sin offering' language in Hebrews often uses peri hamartias (concerning sin / for sin) — the same phrase used in the Septuagint for the Hebrew asham (guilt/trespass offering). Hebrews 10:6 quotes Psalm 40:6 to show that Christ's body was the final peri hamartias. Every preposition in the Greek New Testament carries covenantal weight when placed in service of the atonement.