A.T. Robertson Commentary Galatians 5:2

"Behold, I Paul say unto you, that, if ye receive circumcision, Christ will profit you nothing." — Galatians 5:2 (ASV)

I Paul (εγω Παυλος). Asserts all his personal and apostolic authority. For both words see also 1 Thessalonians 2:16; 2 Corinthians 10:1; Colossians 1:23; Ephesians 3:1.

If ye receive circumcision (εαν περιτεμνησθε). Condition of third class and present passive subjunctive, a supposable case, but with terrible consequences, for they will make circumcision a condition of salvation. In that case Christ will help them not at all.