Bereishis 49:10
לֹא־יָסוּר שֵׁבֶט מִיהוּדָה וּמְחֹקֵק מִבֵּין רַגְלָיו עַד כִּי־יָבֹא שִׁילֹה וְלוֹ יִקְּהַת עַמִּים
The scepter shall not depart from Yehudah, nor the lawgiver from among his descendants, until Shiloh comes, and to him the nations will gather.

On his deathbed Yaakov Avinu blessed his sons, giving each of the twelve tribes its own prophecy: the seeds of the Jewish nation, Bnei Yisrael.
When he blesses Yehudah, Rashi, following Onkelos on this pasuk, explains that the Melech HaMashiach will come from the line of Yehudah. Sefer Shmuel and the Gemara confirm the lineage: Mashiach comes from David, and David from Yehudah.
Did you know that David is actually contained in the name Yehudah? Is it a coincidence? There are no coincidences in the Torah.
David, inside Yehudah
יְהוּדָה → דָּוִד · Bereishis 49:10
Write יְהוּדָה. Remove the first and last letters, and הוּד remains. Now take away the leg of the ה, its short stroke on the left, and it becomes a ד. The letters spell דָּוִד: David.
So David not only descends from Yehudah; he is written into his very name.
More on Yehudah’s name: Yehudah: Our Namesake, Our Essence.
© J.S. Silverstein · Beor Panecha