הַאֶפְשַׁר דִיהַב אוֹרַיְתָא לְעַמֵיהּ וְכַד יְחוֹבוּן הֲלָא יִתְוַכְּחוּן הֲלָא יְיָ אַלִיף לְאָדָם קַדְמַאי מַנְדְעָא.
1. discipline... rebuke | הֲיֹסֵר... יוֹכִיחַ – See Ibn Ezra and Radak that the psalmist is rhetorically asking: "If Hashem has punished multiple nations (the wicked of the Flood, Sedom etc.), will He not rebuke you as well?" Cf. Hoil Moshe that both verbs refer to instruction rather than punishment. Malbim, in contrast, suggests that "יוֹכִיחַ" means "to prove"; Hashem's disciplining of other nations and His teaching of knowledge to mankind should prove to all that He does indeed listen and pay heed.
2. He who teaches man knowledge | הַמְלַמֵּד אָדָם דָּעַת – This phrase appears to be an unfinished thought. See R. Saadia and Metzudat David that the middle clause of the verse, "will He not rebuke", applies to it as well, with the poet rhetorically questioning: if Hashem is the One who disciplines and who teaches right from wrong, is it not self-evident that He shall rebuke those who sin? Alternatively, the conclusion is unstated and simply assumed: "He who teaches man knowledge, will He not know?" (Radak)