δεῖ inf. (τὸ) δεῖν Lk 18:1, Ac 25:24; AcPlCor 1:9, subj. δέῃ, impf. ἔδει (B-D-F §358, 1; Rob. 885f), fut. δεήσει Josh 18:4; impers. verb from δέω; for Attic ins forms s. Threatte II 634f (Hom.+) Strict classification of usage is not possible because of the multifunctional adaptability of this verb, esp. in colloquial discourse.
① to be under necessity of happening, it is necessary, one must, one has to, denoting compulsion of any kind.
ⓐ of that which takes place because of circumstances or inner necessity, with the context determining the cause (Hdt. [8, 53 ἔδεε κατὰ τὸ θεοπρόπιον]; Appian, Liby. 122 §578 ἁλῶναι ἔδει Καρχηδόνα=it was necessary that Carthage be captured, i.e. it could not escape being captured [Appian’s theological perspective surfaces, s. e.g. 7, 53; 8, 51; 57; 61; 62; 92]; Da 2:28f, 45 Theod; Wsd 16:4; Just., D. 6, 2; 32, 4) Mt 17:10; 24:6 (δεῖ γενέσθαι as Jos., Ant. 10, 142); 26:54; Mk 9:11; 13:7, 10; Lk 4:43; 21:9; 24:46 v.l.; J 3:14, 30; 9:4; 10:16; 20:9; Ac 1:16; 3:21; 4:12; Ro 1:27; 1 Cor 15:53; 2 Cor 5:10; Rv 1:1; 4:1; 22:6; 2 Cl 2:5.
ⓑ of the compulsion of law or custom ᾗ ἔδει θύεσθαι τὸ πάσχα when the paschal lamb had to be sacrificed Lk 22:7.—Mt 23:23; Lk 11:42; 13:14; J 4:20, 24; Ac 15:5; 18:21 v.l. Of the compulsion of Roman law 25:10.
ⓒ of an inner necessity growing out of a given situation, Mt 26:35 (Jos., Ant. 6, 108 κἂν ἀποθανεῖν δέῃ; PFay 109, 5 ἐάν σε δῇ [=δέῃ] τὸ εἱμάτιόν σου θεῖναι ἐνέχυρον; Ath. 24, 1 τί δὲ δεῖ πρὸς ὑμᾶς … μνημονεύειν;), Mk 14:31; J 4:4; Ac 14:22; 21:22 v.l.; 27:21; 2 Cor 11:30.—ὥστε … [τὴν Ἀρτεμύλλαν] μικ̣ρ̣ο̣ῦ δεῖν ἀπόπληκτον γενέσθαι so that Artemilla was on the point of fainting AcPl Ha 3, 33–35 (Demosth. 27, 29; Jos., C. Ap. 2, 119 al.).
ⓓ of compulsion caused by the necessity of attaining a certain result Lk 12:12; 19:5; Ac 9:6; 1 Cor 11:19; 2 Cl 1:1; B 4:1; IEph 7:1.—τὰ δέοντα (PPetr II, 11 [1], 6; BGU 251, 5 al.; pap; Pr 30:8; 2 Macc 13:20) the needs Hs 2, 5 and 8.
② to be someth. that should happen because of being fitting,
ⓐ gener. (Epict. 2, 22, 20 φίλος ἔσομαι οἷος δεῖ; 3, 23, 21 ὡς δεῖ, as Just., D. 114, 1; 2 Macc 6:20; 4 Macc 7:8) 2 Ti 2:6, 24. καθὸ δεῖ as is proper Ro 8:26.—δέον ἐστίν it is necessary, one must (Polyb.; POxy 727, 19f; 1061, 13; BGU 981 II, 6; Sir. Prol. ln. 3; 1 Macc 12:11; EpArist) Ac 19:36; 1 Cl 34:2; without ἐστίν (POxy 899, 40; EpArist 227; 242; Philo, Aet. M. 107; Jos., Bell. 2, 296; Just., A I, 4, 6; A II, 2, 7; D. 11, 2) ITr 2:3; Pol 5:3. εἰ δέον ἐστίν if it must be 1 Pt 1:6 (s. εἰμί 11d); οὐ δέον v.l. for οὐδέν Papias (4).—On the constr. of δεῖ, note that as a rule the acc. and inf. follow it (Jos., C. Ap. 2, 254; Lucian, Charon 13, Pisc. 17; Just., D. 11, 2 al.; B-D-F §408), occasionally the inf. alone Mt 23:23 (Jos., C. Ap. 1, 53a; Just., A I, 4, 6 al.—B-D-F §407); 26:54; Ac 5:29.—To convey the idea that someth. should not happen, δεῖ is used w. the negative οὐ Lk 13:16; 2 Tim 2:24; 2 Cl 1:1; AcPlCor 1:10 or μή. Tit 1:11 (ἃ μὴ δεῖ what is not proper [also Ael. Aristid. 54 p. 687 D.] is prob. a mixture of τὰ μὴ δέοντα 1 Ti 5:13 and ἃ οὐ δεῖ [Job 19:4]; s. B-D-F §428, 4; Rob. 1169); Ac 15:24. εἰ δὲ δεῖ ἡμᾶς … μὴ ποιεῖσθαι τὴν παραβολήν AcPlCor 2:28.
ⓑ of that which one should do (Wsd 12:19; 16:28; EpJer 5; Tob 12:1): one ought or should οὐκ ἔδει σε ἐλεῆσαι; should you not have had mercy? Mt 18:33.—Lk 2:49; 15:32; 18:1; Ac 5:29; 1 Th 4:1; Tit 1:11; 1 Cl 62:2.—In τί με δεῖ ποιεῖν; what shall I do? Ac 16:30, δ. stands for the deliberative subj. (B-D-F §366, 4).
ⓒ to indicate that something that happened should by all means have happened, expressed w. the impf. ἔδει (Jos., Bell. 4, 232; Just., D. 88, 6; 141, 1 al.) had to Lk 15:32; 22:7; 24:26; J 4:4; Ac 1:16; 17:3.
ⓓ to indicate that someth. that did not take place really should have happened, also expressed w. the impf. ἔδει should have, ought to have Mt 18:33; 23:23; Ac 24:19 (Ath. 21, 1; ὃν ἔδει w. inf. TestJos 14:3; οὓς ἔδει w. inf.: Isocr. 3, 40, 35a; Lysias 14, 29; Lucian, Philops. 21); 27:21; 2 Cor 2:3. Cp. B-D-F. §358.—EFascher, Theol. Beobachtungen zu δεῖ im AT: ZNW 45, ’54, 244–52, Theol. Beobachtungen zu δεῖ: RBultmann Festschr., ’54, 228–54; CCosgrove, NovT 26, ’84, 168–90 (Luke-Acts).—JKube, ΤΕΧΝΗ und ΑΡΕΤΗ ’69, 46. Cp. χρή. B. 640f. Schmidt, Syn. III 702–5. DELG s.v. δέω 2. EDNT. M-M. TW. Sv.
William Arndt et al., A Greek-English Lexicon of the New Testament and Other Early Christian Literature (Chicago: University of Chicago Press, 2000), 213–214.