(B.T. Vol. N5, p. 228-229.)
From first to last of the words of righteousness on the mountain, the Lord had spoken as none but a divine person was entitled to do.
"And it came to pass, when Jesus concluded these sayings, the crowds were astonished at his doctrine, for he was teaching them as having authority, and not as their scribes."
The Lord, alone on earth, was qualified to speak with authority peculiar to Himself. Beyond all others He knew what was in man (John 2:25): He alone here below knew what was in God (John 3:11). On one side He is the Man whom God raised from out of dead men, marked out by God as judge of living and dead, who will both bring to light the hidden things of darkness and make manifest the counsels of the hearts. On the other hand no one hath seen God at any time, the Only-begotten Son that is in the bosom of the Father — He declared Him. He is thus in every way qualified to speak with authority; yet who so lowly?
But the Jews ware used, now that the Prophets of Jehovah for four centuries had ceased, to lean on their rabbis. Indeed they had shown the same unbelief in the days of prophets of the highest character; as Isaiah bears witness (Isa. 29:13). It was with them in Israel, as afterwards in Christendom, a sea of uncertainty, and a conflict of learned or rash opinions. How could it be otherwise when they were thus cheated to give up God's word for man's ideas? So our Lord cites this very oracle in His day, "In vain they do worship me, teaching as doctrines men's precepts."
But not so the Lord Himself as He sat on the mount, and taught the disciples, within the hearing of the crowds. This Matthew was inspired to present continuously and in orderly relation for permanent use. He began with the characters, the blessed characters, of such as enter the kingdom of the heavens. Four are righteous, three gracious, each class with its consequent persecution, as being in the age where evil still runs on (Matt. 5:3-12). Their position follows, righteous and gracious, toward those outside (13-16).
Then from ver. 17 to the end of the chapter He proceeds to show that far from coming to make void the law or the prophets, He was here to give the fulness of God's mind therein, the light of the kingdom before it is established in any for those who bow to Him. The unbelieving and unsubject shall not enter on the new privileges. Not a tittle should in any way pass from the law till all come to pass. To enter the kingdom a real and inward righteousness, of which Christ is the perfection, must be, far exceeding that of the scribes and Pharisees.
Next He goes farther, not merely "for verily I say to you" (18) and "for I say to you" (20) but with all the emphasis of superior divine light, worthy of God's Son, "Ye heard that it was said to the ancients, Thou shalt not kill … But I say to you" (21-26), and "ye heard that it was said, Thou shalt not commit adultery. But I say to you" (27-30); and incomparably more searching commandments are applied to the law's prohibition of violence and corruption only in their extreme forms.
After that the Lord deals with divorce, and oath in ordinary converse (not judicial), putting all in the same highest place of God's light, with no allowance of human weakness (vers. 31-37). These were matters of righteousness.
In what follows He looks at the higher and deeper claims of grace. Instead of retaliation as in the law of "eye for eye and tooth for tooth," we hear "But I say to you, not to resist evil," etc. (38-42); and instead of "Thou shalt love thy neighbour and hate thine enemy," He urges "But I say to you, Love your enemies, and pray for those who persecute you, that ye may be sons of your Father that is in the heavens," to the point of your being perfect (i.e. in grace), as your heavenly Father is to evil and good, just and unjust (43-48).
In Matt. 6 He points out the true spirit of the life in alms, prayer, and fasting toward God (their Father that seeth in secret before them) (1-18); again in calm confidence above the world's anxiety in ordinary things (19-34): righteousness and grace are here also.
Lastly, in Matt. 7 He guards against evil thoughts of brethren, and communion with the unclean world; and He counsels confiding dependence on their Father, acting toward others as they desired from them, and holding to the narrow gate and the straitened way (1-14). He solemnly warns against false prophets, whose fruits betray them notwithstanding their fair speech (15-20). The vanity of profession without vital reality is pressed even where service and gift are pleaded. It is finally compared to the folly of building on the sand, instead of on the rock of genuine obedience to Christ's words (21-27).
To any anxious soul let me say, Do not mistake. The Lord is not here showing how the sinner is to get pardon and peace. He is teaching His disciples how they are to walk and please their Father. Confusion here denies salvation by grace, is itself mere error, and can only endanger and ruin souls.