Quoting Commentary for I Chronicles 29:10

Ahaziah his son, Joash From Solomon to Joash were eight generations, and since David foresaw that his seed would perish in the days of Joash through Athaliah, as is written in this Book (II Chron. 22:10): “... she arose and destroyed (וַתְּדַבֵּר),” (from the expression of דֶּבֶר pestilence, through poison), he stood in prayer and uttered a psalm (Ps. 12): “For the conductor on the sheminith,” [alluding to an] eight stringed [instrument] (other editions: in number) “for the eighth generation.” (v. 2): “Save, O Lord, for the pious are gone, etc.” And Joash escaped, and from Joash to Josiah are eight generations, for David foresaw that Josiah and his sons would all go to their doom: this one was slain [i.e., Josiah. Perhaps he means Jehoiakim and Zedekiah’s sons as well] and this one’s eyes were gouged out [Zedekiah]. And he [David] prayed again on the sheminith, for the eighth generation (Ps. 6:1f.): “O Lord, do not rebuke me in Your anger,” and because of his prayer, the sons of Jehoiakim survived, and throughout the entire Book of Psalms, there are only these two mentions of the sheminith. And from Jeconiah (other editions: Jehoiakim) until (verse 24): “Anani seven,” which is [an allusion to] the King Messiah, as it is written: (Dan. 7:13): “... and behold, with the clouds of (עֲנָנֵי) the heavens,” are thirty eight sons, including both sons and generations of the sons. The Holy One, blessed be He, did this because he [David] recited thirty eight praises to Him, as it is written in the Book of Ezra (sic) (I Chron. 29:10 13). From “Blessed is the Lord God of Israel, etc.” until “and to strengthen,” are thirty eight words.