פִּ֭י יְדַבֵּ֣ר חָכְמ֑וֹת וְהָג֖וּת לִבִּ֣י תְבוּנֽוֹת׃
My mouth shall speak wisdom, and the meditation of my heart shall be understanding.
Rashi on Psalms
and the thoughts of my heart are understanding The thoughts of my heart are understanding.
Ibn Ezra on Psalms
"My mouth" - to teach all the wisdom hidden from them, which those wise of heart explain by riddles.