The true “Lion and the Lamb” passage is Revelation 5:5-6. 
The Lion and the Lamb both refer to Jesus Christ. 
He is both the conquering Lion of the tribe of Judah and the Lamb who was slain. 
The Lion and the Lamb are descriptions of two aspects of the nature of Christ.  
As the Lion of Judah, 
He fulfills the prophecy of Genesis 49:9 and is the Messiah who would come from the tribe of Judah. 
As the Lamb of God, 
He is the perfect and ultimate sacrifice for sin.