Midrasch zu Schoftim 3:21

Another interpretation (of Jud. 3:16): SO EHUD MADE HIMSELF A SWORD and put it ON HIS RIGHT THIGH. Coming in to Eglon, he said to him: I HAVE A WORD FROM GOD FOR YOU {THE KING}; SO HE AROSE FROM HIS SEAT. The Holy One said: You have imparted glory to me and risen from your seat for the sake of my glory. By your life, I will raise up a daughter from you from whom a son shall arise, and I will seat him upon my throne. This woman was Ruth the Moabite, from whom arose Solomon, of whom it is written (in I Chron. 29:23): THEN SOLOMON SAT UPON THE THRONE OF THE LORD. What is written (in Jud. 3:21)? THEN EHUD PUT OUT HIS LEFT HAND AND TOOK THE SWORD FROM HIS RIGHT THIGH. (Cf. Gen. 49:27, cont.:) IN THE MORNING HE DEVOURS THE PREY. (Jud. 3:21, cont.:) AND HE THRUST IT INTO HIS BELLY. (Cf. Gen. 49:27, cont.:) AND AT EVENING HE DIVIDES THE SPOIL.

He went in to Eglon, and said: “I have a message from God unto thee.” And he arose out of his seat (Judg. 3:20). The Holy One, blessed be He, said to him: You honored Me by arising from your throne; be assured, I will cause your daughter to rear a son who will sit on My throne. This refers to Ruth the Moabitess, from whom Solomon descended. Solomon sat on the throne of the Lord as king (I Chron. 29:23). What is written about Ehud? And Ehud put forth his left hand, and took the sword from his right side, and thrust it into his belly (Judg. 3:21). In the morning he devoureth prey (Gen. 49:27) alludes to the fact that he thrust the sword into his belly; and at even he divideth the spoil refers to the land which he took as spoil.