Jamieson, Fausset and Brown on Isaiah 40:13

13. Quoted in Ro 11:34; 1Co 2:16. The Hebrew here for "directed" is the same as in Is 40:12 for "meted out"; thus the sense is, "Jehovah measures out heaven with His span"; but who can measure Him? that is, Who can search out His Spirit (mind) wherewith He searches out and accurately adjusts all things? Maurer rightly takes the Hebrew in the same sense as in Is 40:12 (so Pr 16:2; 21:2), "weigh," "ponder." "Direct," as in English Version, answers, however, better to "taught" in the parallel clause.