"to mark off by bounds" (apo, "from," horizo, "to determine;" horos, "a limit"), "to separate," is used of "(a) the Divine action in setting men apart for the work of the gospel, Romans 1:1; Galatians 1:15; (b) the Divine judgment upon men, Matthew 13:49; 25:32; (c) the separation of Christians from unbelievers, Acts 19:9; 2 Corinthians 6:17; (d) the separation of believers by unbelievers, Luke 6:22; (e) the withdrawal of Christians from their brethren, Galatians 2:12 . In (c) is described what the Christian must do, in (d) what he must be prepared to suffer, and in (e) what he must avoid."* [* From Notes on Galatians, by Hogg and Vine, p. 83.]
"to put asunder, separate," is translated "to separate" in Romans 8:35,39; in the Middle Voice, "to separate oneself, depart" (see DEPART); in the Passive Voice in Hebrews 7:26 , RV , "separated" (AV, "separate"), the verb here relates to the resurrection of Christ, not, as AV indicates, to the fact of His holiness in the days of His flesh; the list is progressive in this respect that the first three qualities apply to His sinlessness, the next to His resurrection, the last to His ascension. See PUT , No. 14.
"to mark off" (apo, "from," dia, "asunder," horizo, "to limit"), hence denotes metaphorically to make "separations," Jude 1:19 , RV (AV, "separate themselves"), of persons who make divisions (in contrast with ver. 20); there is no pronoun in the original representing "themselves."
"apart from, without" (cp. aneu, "without," a rarer word than this), is translated "separate from" in Ephesians 2:12 (AV, "without"). See APART , BESIDE , WITHOUT.