For the phrase see 1Co 6:9; 1Co 15:33; Jam 1:16. Deceive is a secondary sense; the primary meaning being lead astray. See on Mar 12:24. The connection of the exhortation may be with the entire section from Gal 6:1 (Eadie and Sieffert), but is more probably with Gal 6:6. The Galatians are not to think that it is a matter of no consequence whether their fellowship be with their Christian teachers who preach the word of truth, or with the Judaising innovators who would bring them under bondage to the law.
Is not mocked (οὐ μυκτηρίζεται)
N.T.o. Quite often in lxx. See 1Ki 18:27; 2Ki 19:21; Job 22:19; Pro 1:30. Also the noun μυκτηρισμός mockery, Job 34:7; Psa 34:16. See Ps. of Sol. 4:8. The verb, literally, to turn up the nose at. Comp. Horace, Sat. i. 6, 5, naso suspendis adunco, ii. 8, 64; Epist. i. 19, 45.
That (τοῦτο)
Most emphatic. That and nothing else. Comp. Mat 7:16; 2Co 9:6.