know that they shall die - and may thereby be led “so to number their days, that they may apply their hearts to wisdom” (Ecc 7:1-4; Psa 90:12).
dead know not anything - that is, so far as their bodily senses and worldly affairs are concerned (Job 14:21; Isa 63:16); also, they know no door of repentance open to them, such as is to all on earth.
neither ... reward - no advantage from their worldly labors (Ecc 2:18-22; Ecc 4:9).
memory - not of the righteous (Psa 112:6; Mal 3:16), but the wicked, who with all the pains to perpetuate their names (Psa 49:11) are soon “forgotten” (Ecc 8:10).