Only here and 2Co 11:26. Christians in name only; Judaisers; anti-Paulinists. The article marks them as a well known class.
Unawares brought in (παρεισάκτους)
N.T.o. Lit. brought in by the side, and so insidiously, illegally. Vulg. subintroductos. olxx. Strabo (xvii. 1) uses it as an epithet of Ptolemy, “the sneak.” Comp. παρεισάξουσιν shall privily bring in, 2Pe 2:1; and παρεισεδύησαν crept in privily, Jud 1:4. Brought in, not from Jerusalem into the church at Antioch, nor into the Pauline churches generally, but into the Christian brotherhood to which they did not rightfully belong.
Who (οἵτινες)
The double relative introduces the explanation of the two preceding epithets: false brethren, privily brought in, since they came in privily to spy out our liberty.
Came in privily (παρεισῆλθον)
Lit. came in beside. Only here and Rom 5:20, where it implies nothing evil or secret, but merely something subsidiary. The aorist has a pluperfect sense, indication the earlier intrusion of these persons into the Christian community.
To spy out (κατασκοπῆσαι)
N.T.o. In lxx, of spying out a territory, 2Sa 10:3; 1Ch 19:3.
Liberty (ἐλευθερίαν)
Freedom from Mosaism through justification by faith.
Bring us into bondage (καταδουλώσουσιν)
Only here and 2Co 11:20. Bring us into subjection to Jewish ordinances. The compound verb indicates abject subjection.