if. The Hebrew Accent (Pashta) puts the emphasis on the 1st "well" and on this 2nd "if", to mark the solemn and Important alternative.
sin = sin offering. Hebrew. chata. See App-43. The word "offering" is actually added in Exo_30:10. Lev_4:3, Lev_6:25; Lev_8:2. Psa_40:6. Compare 2Co_5:21. Eph_5:2.
lieth. Lieth is mase. Sin offering is feminine. So that the Hebrew reads "at the entrance [a male] is lying, a sin offering".