Three things jump out of these verses:
One: “leave his father and his mother…”
We see here at the creation of humanity, that the family is also established. Man and woman, father and mother, are needed to accomplish God’s command. The one we saw back in the first account when He created humanity. But this also isn’t a huge, generations-long family even though that is not negated here. We are looking at the nuclear family. A husband, a wife, and their kids. There is importance in each couple striking out and becoming their own special unit.
Two: “…become one flesh.”
Each couple is a unit, the best expression of what humanity can be. Even though each individual is special and God-created for a relationship with Him, humanity is best seen as the blend of male and female. Outside of a select number of people for whom God’s best plan involves remaining single, we are at our best when we are tempered by our “other half.” And, in sin this has become more of a challenge, but the sense was always to yield and benefit from the other perspective. Men and women naturally emphasize different aspects of life, but we need the emphasis of the other half to be at our best.
In some sense, this is a chief concern with homosexuality. For some it is easier to latch on to the “self” to the unchallenging comfort of never being faced with the views and values of the opposite sex. But from the beginning, God’s design has humanity incomplete without both halves, the male and the female. Some rightly say that homosexuality is a perversion of God’s design. It is also a tragic destruction of the wholeness God intended for His people.
Three: “…naked and were not ashamed.”
The key here is the shamelessness, not the nudity. I for one suspect that nudity was not necessarily God’s permanent intention. Just as He wanted humanity to choose good—His way—and not remain merely innocent for all of eternity, He might have planned for us to discover fashion for all the right reasons. Regardless, the issue here is that the man and woman had the perfect relationship. They were perfectly intimate and unreserved, uncomplicated. There were no insecurities, not doubts, no secrets. Later, when sin enters the picture this relationship will be one of the many destroyed and it is a tragedy. How amazing would it be to be able to relate to people in this way today? Even in the best of marriages this is beyond us now.