18. For verily I say unto you--Here, for the first time, does that august expression occur in our Lord's recorded teaching, with which we have grown so familiar as hardly to reflect on its full import. It is the expression manifestly, of supreme legislative authority; and as the subject in connection with which it is uttered is the Moral Law, no higher claim to an authority strictly divine could be advanced. For when we observe how jealously Jehovah asserts it as His exclusive prerogative to give law to men (Le 18:1-5; 19:37; 26:1-4, 13-16, &c.), such language as this of our Lord will appear totally unsuitable, and indeed abhorrent, from any creature lips. When the Baptist's words--"I say unto you" (Mt 3:9) --are compared with those of his Master here, the difference of the two cases will be at once apparent.
      Till heaven and earth pass--Though even the Old Testament announces the ultimate "perdition of the heavens and the earth," in contrast with the immutability of Jehovah (Ps 102:24-27), the prevalent representation of the heavens and the earth in Scripture, when employed as a popular figure, is that of their stability (Ps 119:89-91; Ec 1:4; Jer 33:25, 26). It is the enduring stability, then, of the great truths and principles, moral and spiritual, of the Old Testament revelation which our Lord thus expresses.
      one jot--the smallest of the Hebrew letters.
      one tittle--one of those little strokes by which alone some of the Hebrew letters are distinguished from others like them.
      shall in no wise pass from the law, till all be fulfilled--The meaning is that "not so much as the smallest loss of authority or vitality shall ever come over the law." The expression, "till all be fulfilled," is much the same in meaning as "it shall be had in undiminished and enduring honor, from its greatest to its least requirements." Again, this general way of viewing our Lord's words here seems far preferable to that doctrinal understanding of them which would require us to determine the different kinds of "fulfilment" which the moral and the ceremonial parts of it were to have.

JFB.