1 Peter 2:25

25 For you were continually straying like sheep, but now you have returned to the Shepherd and Guardian of your souls.

Peter may have been thinking of Isaiah 53:6, referring to our unregenerate condition, as sheep without a shepherd, unguided and unprotected from evil. But when we gave our heart to Him we repented of our sinful ways and started following Him as our Shepherd and Guardian. As our Shepherd He watches over us, guides us, and leads us in the paths of righteousness (Ps. 23). As our Guardian He is our good protector from evil, keeping our soul protected forever.