Probably from phule through the idea of isolation; to watch, i.e. Be on guard (literally of figuratively); by implication, to preserve, obey, avoid -- beward, keep (self), observe, save. Compare tereo.

see GREEK phule

see GREEK tereo

1. Active, to guard (Latincustodio); i. e., a. to watch, to keep watch: with φυλακήν, added, Luke 2:8 (see φυλακή, a.).

b. to guard or watch, have an eye upon: τινα, one, lest he escape, Acts 12:4; Acts 28:16; passive, Acts 23:35; Luke 8:29; τί, anything, lest it be carried off: τά ἱμάτια, Acts 22:20.

c. to guard a person (or thing) that he may remain safe, i. e. lest he suffer violence, be despoiled, etc., equivalent to to protect: τήν αὐλήν, Luke 11:21; ἀπό τίνος, to protect one from a person or thing, 2 Thessalonians 3:3 (see πονηρός, p. 531a) (Xenophon, Cyril 1, 4, 7; Psalm 140:9 (); cf. Buttmann, § 147, 3; (Winer's Grammar, 223 (209))); τήν παραθήκην (or παρακαταθήκην), to keep from being snatched away, preserve safe and unimpaired, 1 Timothy 6:20; 2 Timothy 1:14; with the addition of εἰς τινα ἡμέραν, i. e. that it may be forthcoming on that day, 2 Timothy 1:12; to guard from being lost or perishing, i. e. (with the predominant idea of a happy issue), to preserve: τινα, John 17:12 (where ἐφύλαξα is explained by the following οὐδείς ἐξ αὐτῶν ἀπώλετο (cf. τηρέω, at the end)); 2 Peter 2:5; τινα with a predicate accusative, Jude 1:24; φυλάξει (opposed to ἀπολέσει) τήν ψυχήν εἰς ζωήν αἰών. i. e. will keep it with the result that lie will have life eternal, John 12:25; ἑαυτόν ἀπό τόν to guard oneself from a thing, 1 John 5:21 (where cf. Westcott).

d. to guard, i. e. to care for, take care not to violate; to observe: τόν νόμον, Acts 7:53; Acts 21:24; Galatians 6:13 (Leviticus 19:37, etc.; Sophocles Trach. 616; others; νόμους, Xenophon, Hell. 1, 7, 30; Plato, de rep. 6, p. 484 b.; polit., p. 292 a.); single precepts of the Mosaic law, Matthew 19:20 L T Tr WH; Mark 10:20 Lachmann; Luke 18:21 L T Tr text WH; (τά δικαιώματα τοῦ νόμου, Romans 2:26); τόν λόγον τοῦ Θεοῦ, Luke 11:28; τά ῤήματα of Jesus, John 12:47 L T Tr WH; apostolic directions, Acts 16:4; 1 Timothy 5:21.

2. Middle a. to observe for oneself something to escape, i. e. to avoid, shun, flee from: by a use common in Greek writings from Aeschylus and Herodotus down, with an accusative of the object, τί, Acts 21:25 (A. V. keep themselves from); τινα, 2 Timothy 4:15 (A. V. be thou ware of); ἀπό τίνος, to keep oneself from a thing, Luke 12:15 (Xenophon, Cyril 2, 3, 9; (Hell. 7, 2, 10)); ἵνα μή, 2 Peter 3:17 (ὅπως μή, Xenophon, mem. 1, 2, 37; other examples in Passow, under the word, p. 2360{a}; (Liddell and Scott, under the word, C. II.)).

b. by a usage foreign to Greek writings but very frequent in the Sept. (cf. Winers Grammar, 253 (238)), to guard for oneself (i. e. for one's safety's sake) so as not to violate, i. e. to keep, observe: ταῦτα πάντα (the precepts of the Mosaic law), Matthew 19:20 R G; Mark 10:20 R G T Tr WH; Luke 18:21 R G Tr marginal reading (Exodus 12:17; Leviticus 18:4; Leviticus 20:8, 22; Leviticus 26:3, and many other passages). (Compare: διαφυλάσσω. Synonym: see τηρέω, at the end.)