The reason is here given why investigation into man’s “works” is only “sore travail” (Ecc 1:13); namely, because all man’s ways are vain (Ecc 1:18) and cannot be mended (Ecc 1:15).
vexation of - “a preying upon”
the Spirit - Maurer translates; “the pursuit of wind,” as in Ecc 5:16; Hos 12:1, “Ephraim feedeth on wind.” But old versions support the English Version.