[papertyger]

why not a word about it in the New Testament?

There's no need for it in the New Testament. It's in God's Word through Holy Tradition.

[Petronski]

Did you know that the Ten Commandments do not appear in the New Testament?

Then again, perhaps when one is “ELECT” (with or without the vanity plates), there is no longer any use for them (!?!).

[AnalogReigns]

So here we have a very important essential practice which all the Apostles in writing the foundational documents of the Church simply forgot about.

Goodness, thanks be to God that there’s a human institution still around conveying tradition to correct them! /s