New Defender's Study Bible Notes
3:20 of the dust. This statement merely refers to the universal curse pronounced by God on man and all his dominion because of sin. Both men and beasts were made out of the basic elements, the “dust of the ground,” and their bodies return to dust again at death. This principle is expressed scientifically as the law of increasing entropy. See on Genesis 3:17-19.
3:21 goeth upward. “Spirit” is the same word as “breath”; in this sense, both men and beasts have “spirit,” but the breathing apparatus ceases to function at death. “Spirit” may also refer to that aspect of man which communicates with God’s Spirit, and which returns to God at death (Ecclesiastes 12:7). Animals do not have this.