Ambrose of Milan

It is written in the book of the prophet, "Take a branch from a nut tree." So we must consider why the Lord said this to the prophet, for it is not written without a purpose, since we also read in the Pentateuch that the nut tree of Aaron, the priest, blossomed after it had been laid away for a long while.

Letter 62 ↗

Jerome

And the word of the Lord came to me, saying: What do you see, Jeremiah? And I said, I see a watching rod. And the Lord said to me: You have seen well, for I will watch over my word to perform it. For the watching rod, the Septuagint translated it as a nut-stick. Therefore, we must work so that the Latin reader understands the Hebrew etymology briefly. Seced is called a nut: but watching or watch or to watch is called Soced. And in the later [books], the leopard is placed in this position as a vigilant guardian. …

Commentary on Jeremiah ↗

Bonaventure

In the mystery of prophetical revelation, Christ is symbolized especially by means of sight. The prophet saw "a branch of the watching-tree." Christ is symbolized through prophetical visions, and this in different ways: for one saw Christ as "a branch of the watching-tree," another saw Him "seated on a high and lofty throne," while yet another saw Him "dressed."

Collations on the Hexaemeron, Collation 14 ↗