oath

Boyd’s Bible Dictionary:

Appeals to God to attest the truth of an assertion in early use
(Gen. 21:23; 26:3; Heb. 6:16). Regulated in Ex. 20:7; Lev. 19:12. Forms: lifting hands (Gen. 14:22); placing hand under thigh (Gen. 24:2); before the altar (1 Kings 8:31); laying hand on the law.

Concise Bible Dictionary:

A solemn asseveration with an appeal to God that what is said is true. The apostle said that among men an oath for confirmation is the “end of all strife” or dispute; and God, willing to show “the immutability of his counsel, confirmed it by an oath; that by two immutable things [His word and His oath] in which it was impossible for God to lie, we might have a strong consolation” (Heb. 6:16-18). Jehovah swore that the Lord Jesus should be a priest forever after the order of Melchizedek (Psa. 110:4).
Leviticus 5:1 has been interpreted as signifying that when the voice of adjuration was heard, persons were compelled to confess what they knew as to any charge. Thus the Lord Jesus when adjured by the high priest answered him. The Lord was under an accusation, and was adjured to say if it was true. He acknowledged that He was “the Christ the Son of God” (Matt. 26:63-64).
The Lord exposed the folly of the tradition that some oaths were not binding (Matt. 23:16-22).
In the common intercourse of life there should be no oaths, the simple “yea” and “nay” should be enough, “swear not at all” (Matt. 5:34-37; James 5:12): the context of these passages shows that they do not refer to judicial oaths (compare also Heb. 6:13,16; Heb. 7:21; Rev. 10:6).

Strong’s Dictionary of Greek Words:

Greek:
ὁρκωμοσία
Transliteration:
horkomosia
Phonic:
hor-ko-mos-ee’ah
Meaning:
from a compound of 3727 and a derivative of 3660; asseveration on oath
KJV Usage:
oath