Isaiah 40:13

מִי־תִכֵּן אֶת־רוּחַ יְהוָה וְאִישׁ עֲצָתוֹ יוֹדִיעֶנּוּ׃

13 Who has set bounds on the mind of the LORD, or who, as a man of advice, has given him instruction?

מִי־תִכֵּן אֶת־רוּחַ יְהוָה Who has set bounds on the mind of the LORD, תִכֵּן is a piel perfect from תָּכַן, "to regulate, measure." The idea of the word in the piel is to "put straight" or "arrange in order." Brown-Driver-Briggs' inclusion of the related Assyrian adjective takânu "be well-ordered" is helpful. The elementary meanings of רוּחַ are of course "breath," "wind" or "spirit," but the parallel phrase is about instruction, and the mind is the part of a man which can receive instruction. The idea of "mind" or "disposition" is also present in 1 Kings 21:5 ("How is it that your spirit is so sullen?" NASB), Joshua 2:11; Psalm 32:2 and Proverbs 16:32. As in verse 12, an Mp note tells us that the piel imperfect תִכֵּן occurs three times (Job 28:25 is the third). There is not dagesh lene in the taw here (a begad-kepat letter) because the word is affixed to מִי with maqqef and therefore the taw has a vowel preceding and loses its dagesh lene (cf. Weingreen's grammar, pages 12 and 112).

The interrogative מִי governs both halves of the verse. This is not unique: Job 6:8; Isaiah 41:2, etc.

וְאִישׁ עֲצָתוֹ יוֹדִיעֶנּוּ׃ or who, as a man of advice, has given him instruction? יוֹדִיעֶנּוּ is a hifil imperfect with a 3rd m. sg. suffix, "who has caused him to know anything?" or "who has given him instruction?" This word by itself would have been sufficient for the parallelism, but Isaiah has set down another term, אִישׁ עֲצָתוֹ, which we just drop into a a clause beginning with "like" or "as," e.g., "who, as a man of advice." The words are drawn together with their accents, merka and tipha. Except for legarmeh (as in Isaiah 39:3), merka only serves tipha and silluq.

The picture for us here is partly of man as librarian( attempting to catalogue the countless volumes in the mind of the Lord), and partly a shake of the head at man as physcoanalyst (or even as dogmatician?), taking notes about God on a yellow legal pad as the Lord lies back on a leather couch under abstract paintings in which he sees the תֹהוּ וָבֹהוּ of the first day of creation. We cannot advise the Lord; we must take the Lord himself as our Chief Advisor. In fact, we humbly and thankfully take our Lord as our Prophet, Priest and King.