Ecclesiastes 3:21 - Ellicott's Commentary On The Whole Bible

The LXX., followed by a great body of interpreters, ancient and modern, translate, “Who knoweth whether the spirit of man goeth upward?” &c, and this agrees better with the context of this paragraph. The sceptical thought is, “We see that death resolves into dust (Genesis 3:19; Ecclesiastes 12:7; see also Sir. 41:10) the bodies of men and animals alike; and if it be alleged that there is a difference as to what becomes of their spirits, can this be asserted with the certainty of knowledge?” The writer here seems to have read both Psalms 49:14 and Proverbs 15:24.