Nehemiah 4:3 (BSB)

Then Tobiah the Ammonite, who was beside him, said, “If even a fox were to climb up on what they are building, it would break down their wall of stones!”

From Nehemiah 4. Also in the ESV.

Commentary on Nehemiah 4:3

• Matthew Henry (Presbyterian), Matthew Henry's Complete Commentary on Nehemiah 4:1-6: Here is, I. The spiteful scornful reflection which Sanballat and Tobiah cast upon the Jews for their attempt to build the wall about Jerusalem. The country rang of it presently; intelligence was brought of it to Samaria, that nest of enemies to the Jews and their prosperity; and here we are told how they received the tidings. 1. In heart.
• John Gill (Reformed Baptist), Exposition of the Old and New Testaments on Nehemiah 4:3: Now Tobiah the Ammonite was by him,.... Who was one of his brethren he spake before, Neh 4:2, and he said; in the like contemptuous and scoffing manner: even that which they build, if a fox go up, he shall break down their stone wall; signifying not only that it was so low that a fox could easily get up to it, or leap over...
• Jamieson-Fausset-Brown (Reformed), Commentary Critical and Explanatory on the Whole Bible on Nehemiah 4:3: if a fox go up--The foxes were mentioned because they were known to infest in great numbers the ruined and desolate places in the mount and city of Zion (Lam 5:18).
• Keil & Delitzsch (Lutheran), Biblical Commentary on the Old Testament on Nehemiah 4:3: Neh 4:3 (Hebrew_Bible_3:35) Tobiah the Ammonite, standing near Sanballat, and joining in in his raillery, adds: “Even that which they build, if a fox go up he will break their stone wall;” i.e., even if they build up walls, the light footsteps of the stealthy fox will suffice to tread them down, and to make breaches in their work.