See the notes at Matthew 23:29-36.

Ye build the sepulchres - That is, ye rebuild and beautify them. See on Matthew 23:29 (note).

(15) Woe unto you! for ye build the sepulchres of the prophets, and your fathers killed them.
(15) Hypocrites honour those saints when they are dead whom they persecute most cruelly when they are alive.

Woe unto you,.... Meaning particularly the lawyers or Scribes, together with the Pharisees, and even the whole body of the people, who in general were of the cast and complexion here described:
for ye build the sepulchres of the prophets; See Gill on Matthew 23:29.
and your fathers killed them; the prophets; "or whom your fathers killed", as read the Syriac, Arabic, and Persic versions; the one put them to death, and the other erected stately monuments over them, or adorned them; and yet both had the same malignant spirit against the faithful servants and messengers of God; and which showed their great hypocrisy.

ye build, &c.--Out of pretended respect and honor, they repaired and beautified the sepulchres of the prophets, and with whining hypocrisy said, "If we had been in the days of our fathers, we should not have been partakers with them in the blood of the prophets," while all the time they "were witnesses to themselves that they were the children of them that killed the prophets" (Matthew 23:29-30); convicting themselves daily of as exact a resemblance in spirit and character to the very classes over whose deeds they pretended to mourn, as child to parent.