The words δεῖ, ὀφείλω (ὀφείλω) and χρή are all translated 'ought,' with other variations as to the first two. But there is a difference in their signification. Bengel says ὀφείλω denotes ‘obligation;' δεῖ ‘necessity.' ὀφείλω is to be under moral obligation, bound by duty, one ought, &c., and specially in personal aspects. See Eph. 5:28; 2 Cor. 12:11, 14; Acts 17:29; Rom. 15:1; 1 John 2:6; 3:16; 4:11. Compare Luke 11:4 ‘indebted,' Matt. 18:28, 30. ὀφείλω (with its compounds) is with one exception the word for 'owing,' and what is owed, Philem. 1:18; Rom. 13:8; 15:27, 27, translated ‘debtor' and ‘duty.' In Luke 17:10 it is "that which was our duty": Heb. 2:17, "it behooved him": 2 Thess. 1:3; 2:13, "are bound."
δεῖ is more general, denoting any kind of necessity, as that which lies in the nature of the case, or specially that which arises by divine appointment, and this gives it a greater strength: ‘must' is its most frequent rendering. See 2 Tim. 2:6; Luke 22:7; John 3:7, 14, 30; 4:4 ('must needs'), 24; Acts 16:30 Cor. 15:53; Heb. 9:26; 11:6; Mark 14:31 ('should,’ ‘should have to'); Acts 5:29 ‘ought.' These may illustrate the general use, and the following passages, out of many, the necessity established by the will and word of God: Mat. 16:21; 17:10; 14: 6; 54; Luke 2:49; 4:43; 22:37; 24:7, 26 ('ought'), 44; John 9:4; 20:9; Acts 1:16, 22 (21); 3:21; 4:12; 9:16; 14:22; 23:11; 24; 1 Cor. 15:25; 2 Cor. 5:10; 1 Tim. 3:7; Rev. 1:1.
χρή occurs but once, Jas. 3:10: coming from the root of χράω,’ to deliver an oracle,’ 'to be fated,' it passes into the sense of what is necessary, what behooves or is fitting (or the reverse with οὐ, negative, as in Jas. 3:10). Compared with the other words, it is rather a necessity of time or circumstance, and has not the same moral force. Compare the kindred verb χρῄζω (from χρεία ‘need, necessity '): ‘to have need of,'
Matt. 6:32; Rom. 16:2; need,' Luke 11:8; 2 Cor. 3:1.