Oath - Vine's Expository Dictionary of New Testament Words
Oath[ 1,,G3727, horkos ]
is primarily equivalent to herkos, a fence, an enclosure, that which restrains a person;" hence, "an oath." The Lord's command in Matthew 5:33 was a condemnation of the minute and arbitrary restrictions imposed by the scribes and Pharisees in the matter of adjurations, by which God's Name was profaned. The injunction is repeated in James 5:12. The language of the Apostle Paul, e.g., in Galatians 1:20; 1 Thessalonians 5:27 was not inconsistent with Christ's prohibition, read in the light of its context. Contrast the "oaths" mentioned in Matthew 14:7, Matthew 14:9; Matthew 26:72; Mark 6:26.
Hebrews 6:16 refers to the confirmation of a compact among men, guaranteeing the discharge of liabilities; in their disputes "the oath is final for confirmation." This is referred to in order to illustrate the greater subject of God's "oath" to Abraham, confirming His promise; cp. Luke 1:73; Acts 2:30. Cp. the verbs horkizo, and exorkizo, under ADJURE.
[ 2,,G3728, horkomosia ]
denotes "an affirmation on oath" (from No. 1 and omnumi, "to swear"). This is used in Hebrews 7:20-Hebrews 7:21 (twice), Hebrews 7:28 of the establishment of the Priesthood of Christ, the Son of God, appointed a Priest after the order of Melchizedek, and "perfected for evermore." In the Sept., Ezekiel 17:18-Ezekiel 17:19.
Note: For anathematizo in Acts 23:21, AV, "have bound (themselves) with an oath," See CURSE.