Easton's Bible Dictionary (1897)
Used only in Gal. 4:24, where the apostle refers to the history of Isaac the free-born, and Ishmael the slave-born, and makes use of it allegorically. Every parable is an allegory. Nathan (2 Sam. 12:1-4) addresses David in an allegorical narrative. In the eightieth Psalm there is a beautiful allegory: “Thou broughtest a vine out of Egypt,” etc. In Eccl. 12:2-6, there is a striking allegorical description of old age.
Smith's Bible Dictionary (1863)
”—Encyc. ) In every allegory there is a twofold sense—the immediate or historic, which is understood from the words, and the ultimate, which is concerned with the things signified by the words. The allegorical interpretation is not of the words, but of the thing signified by them, and not only may, but actually does, coexist with the literal interpretation in every allegory, whether the narrative in which it is conveyed be of things possible or real.
An illustration of this may be seen in (Galatians 4:24) where the apostle gives an allegorical interpretation to the historical narrative of Hagar and Sarah, not treating that narrative as an allegory in itself; as our Authorized Version would lead us to suppose, but drawing from it a deeper sense than is conveyed by the immediate representation.
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
AL'LEGORY. Gal 4:24. A figure of speech, nearly resembling the parable or fable, common in the Scriptures and among all Oriental nations. It properly means a figurative speech which, under the literal sense of the words, conveys a deeper spiritual meaning. But the literal or historic sense is not necessarily denied. Paul gives two examples of allegorical interpretation — the rock in the wilderness of which the Israelites did drink, and which spiritually or mystically means Christ, 1 Cor 10:4 ; and the story of Hagar and Sarah. Gal 4:24, Gal 4:25. In v.
25 the best critical authorities leave out "Agar," and thus rid the verse of much of its difficulty, for it is not asserted that Agar is, but that Sinai is, a mountain in Arabia. See Parable.