What is all the Law and all the commandments fulfilled in?
All the Law and all the commandments are fulfilled in one word: agape love. This is God-given love that always seeks the other person's highest good, rather than using liberty to satisfy the lusts of the flesh. It is the word in the Greek, agape.
Les explains that the Law and commandments are fulfilled in one word, and that word is agape love. He defines agape as seeking the other person's highest good under every circumstance, even selling ourselves short for the other's benefit. Instead of using our liberty as an occasion to satisfy the lusts of the flesh, we are to let God-given agape love guide us. Les contrasts this with Peter, who used phileo, a lesser term, when he said he was fond of Jesus. He also encourages comparing Scripture with Scripture, as Paul writes in Romans chapter 13, so we don't dismiss what it plainly says.
For all the law is fulfilled in one word, even in this; Thou shalt love thy neighbour as thyself.