Is plastic surgery a sin?
It depends on the situation, and more specifically the purpose behind wanting the procedure. Is one going under the plastic surgeon’s knife out of medical or psychological necessity? For example, to repair a damaged facial structure obtained from an injury and thus gain back self-confidence and physical ability, or some other type of medical or psychological need? I find nothing in Scripture to prohibit that.
On the other hand, is one having the procedure out of a desire to be sexually alluring? Is one wanting plastic surgery out of inherent vanity? There are scriptural principles which would speak against that (1 Tim. 2:9-10; 1 Pet. 3:3-4; Matt. 18:6-9), and one would be prudent to heed those principles should they be relevant to one’s reasons for wanting the procedure.
God knows the reasons behind one’s decision to undergo plastic surgery, and many times other people do not know those reasons. We must not judge according to appearance, but judge with right judgment (John 7:24). Love would give others the benefit of the doubt rather than make a negative assumption as to why they would do something that may seem on the surface to be questionable (1 Cor. 13:7), and the Bible does condemn being a meddlesome busybody (2 Thess. 3:11; 1 Tim. 5:13; Prov. 26:17). It would be better for us all to encourage and support each other instead of unrighteously judge or devour each other when we likely do not know the reasons behind the decisions others make.