The first clause of Isaiah 11:3 is translated in various ways: “He will delight” (NASB; NIV; ESV); “He will make him of quick understand” (AV). But the verb is the verbal form of “spirit” ( ruach ) and means to breathe, blow, or, most often, to smell. Yahweh scents the aroma of Noah’s offering (Isaiah 8:21), something idols are incapable of doing since they have noses but no ability to ruach (Psalm 115:6). “He will smell him in the fear of Yahweh” is a preferable, if more opaque, translation.
The clause links the Spirit’s equipment mentioned in verse 2 with the Branch’s work as a judge in the following verses. With the Spirit resting on Him, the Branch will sniff out the fear of Yahweh, judging not by eyes or ears but by His nose. He will judge in favor of the poor whose give off the aroma of the fear of Yahweh.
The Branch breathes in in fear; He breathes out a killing breath ( ruach , v. 4) against the wicked. He delights in the soothing aroma of the sacrifice of righteousness; He breathes the fire of the Spirit to kill the unjust.