Extended Strong's Greek Lexicon (Abbott-Smith based)
unbelief
Usage: ἀπιστία, -ας, ἡ (ἄπιστος), [in LXX: Wis.14:25, 4Ma.12:4 * ;] want of faith, unbelief: Mat.13:58, Mrk.6:6 9:24 16:14, Rom.3:3 (but see: ἀπιστέω) Rom.4:20 11:20, 23, 1Ti.1:13, Heb.3:12, 19 (DCG, ii, 775a; Cremer, 492).† (AS)