הָבַל verb denominative act emptily, become vain —

Qal Jeremiah 2:5 = 2 Kings 17:15 they went after vanity וַיֶּהְבָּ֑לוּ and became vain, Psalm 62:11 וּבְגָזֵל אַלתֶּֿהְבָּ֑לוּ do not become vain (i.e. be demoralized) by robbery; with cognate accusative Job 27:12 לָמָּה זֶה הֶבֶל תֶּהְבָּ֑לוּ why do ye become vain with vanity (i.e. shew yourselves utterly vain) ?

Hiph`il cause to become vain Jeremiah 23:16 (of false prophets) מַהְבִּלִים הֵמָּה אֶתְכֶם i.e. fill you with vain hopes.

וַיֶּהְבָּ֔לוּ וַיֶּהְבָּֽלוּ׃ ויהבלו ויהבלו׃ מַהְבִּלִ֥ים מהבלים תֶּ֫הְבָּ֥לוּ תֶּהְבָּֽלוּ׃ תהבלו תהבלו׃ mah·bi·lîm mahbiLim mahbilîm teh·bā·lū tehBalu tehbālū vaiyehBalu way·yeh·bā·lū wayyehbālūInterlinear Greek • Interlinear Hebrew • Strong's Numbers • Englishman's Greek Concordance • Englishman's Hebrew Concordance • Parallel Texts