This passage records the establishing of several different precedents by God Himself. Most obviously: the holy Sabbath (verse 3), the sanctity of labor (verse 15), the necessity of faith (verses 16-17), mankind's exercise of freewill (verse 19) and the institution of marriage (verses 22-25).
Why is it that we (in Christendom) struggle with some of these most basic of doctrines... and the applications of them? It makes plenty of sense that Satan would attack these things; but resistance against them from professing Christians?!
1. The Sabbath: many of us are 24/7 type people; acting as if a day of rest is no longer necessary, required, or beneficial. Yet this is the earliest, if not the only commandment from the Decalogue that was instituted prior to the fall of mankind.
2. Work: it's not a curse. The pains and difficulties and failures in labor are a result of the curse, but work itself is not. Responsibilities in labor also preceded the fall.
3. Faith: Hebrews 11:6, "Without faith it is impossible to please God." In every era in history, trust is the foundation of the human/divine relationship.
4. Freewill: though the word first arises in Leviticus 22:18, the first example of it is here. When God created us in His image, He gave us autonomy. It is our most valuable possession… and the one we abuse the most.
5. Marriage: under attack from every imaginable direction, it's still the most sacred human relationship. Sex, matrimony, family, conjugal love... all God's brilliant ideas.
"As for God, His way is perfect ..." (Psalm 18:30). We can never improve upon His plans. We can only comply with them... or resist them. Solomon said it this way, "God has made man upright; but they have sought out many inventions" (Ecclesiastes 7:29).