Barbara from Florida asked, In Rev. 5:5 why is Jesus called “the Lion of Judah”?
To answer your question we need to go back to the Old Testament. We read this in the book of Genesis:
 “Judah, your brothers shall praise you; your hand shall be on the neck of your enemies; your father’s sons shall bow down before you.  Judah is a lion’s cub; from the prey, my son, you have gone up. He stooped down; he crouched as a lion and as a lioness; who dares rouse him?  The scepter shall not depart from Judah, nor the ruler’s staff from between his feet, until tribute comes to him; and to him shall be the obedience of the peoples.  Binding his foal to the vine and his donkey’s colt to the choice vine, he has washed his garments in wine and his vesture in the blood of grapes.  His eyes are darker than wine, and his teeth whiter than milk. (Genesis 49:8–12 ESV)
In that passage, Jacob was is giving a prophetic addresses to each of his sons. When he came to Judah, he said that one would come from that tribe and would reign forever. Jacob used the imagery of a lion to refer to this ruler. Lions are strong and powerful and greatly feared. Hardly anyone would dare to mess with them.
So, when Jesus is called “the Lion of Judah” it is because He's the fulfillment of that prophecy. He's the promised one who reigns forever, strong a powerful like a lion.
Thanks for your question,