12 Therefore, whatever you want men to do to you, do also to them, for this is the Law and the Prophets.
13 “Enter by the narrow gate; for wide is the gate and broad is the way that leads to destruction, and there are many who go in by it.
14 Because narrow is the gate and difficult is the way which leads to life, and there are few who find it.
therefore (v.12) — referring back to giving good gifts in verses 9-11
This is the law and the prophets (v.12) — this is the focus of the Old Testament. As with most of the sermon, verse 12 is explaining God’s standards of righteousness, which nobody can keep.
Hillel, Socrates, Aristotle and Confucius all said similar things before Christ said this (v.12), but their statements were negative and passive where Christ’s is positive and active.
The golden rule is a wonderful standard to live by — far above anything ever attained by this world, yet it does not rise to the heights of grace. Rather “this is the law and the prophets.”
We, the members of the Body of Christ are told to “be kind to one another,” forgiving others — not as others have forgiven us, but “as God, for Christ’s sake, hath forgiven [us]” (Ephesians 4:32).
Further the Law provided no power to carry out the golden rule, but we are told again and again to fulfill the precepts of grace “according to the power of God that worketh in us” (Ephesians 1:18-19; 3:20; 2 Timothy 1:7-8). — Stam, page 103.
The gate (door) and the way is Christ Himself. “I am the door of the sheep; by Me if any man enter in, he shall be saved” (John 10). “I am the way … no man cometh unto the Father but by Me” (John 14). And why then is the gate narrow? Not because certain conditions and hard terms are to be fulfilled, but because man does not want to give up his own righteousness and clinging still to his miserable, filthy rags, he refuses God’s way and God’s door of salvation, which is Christ and Christ alone. — Gaebelein, pages 156-157.