Matthew 23:29

Ye build the tombs of the prophets - That is, you build sepulchres or tombs ever the prophets that have been slain. This they did professedly from veneration and respect for their character. This is often done at the East at the present day, and indeed elsewhere. Among the Muslims it is a common way of showing respect for any distinguished man to build a tomb for him. By doing this, they profess respect for his character and veneration for his memory. So the Pharisees, by building tombs in this manner, professedly approved of the character and conduct of the prophets, and disapproved of the conduct of their fathers in killing them.

And garnish ... - That is, adorn or ornament. This was done by rebuilding them with more taste, decorating them, and keeping them neat and clean. The original word means, also, to show any proper honor to the memory of the dead, as by speaking well of them, praying near them, or rearing synagogues near them in honor of their memory.