Sheep, left to themselves, will wander.  Although they like the security of being led, they are also independent animals.  Some will easily forget where they are and roam, and others will follow them until they are away from their shepherd and be at risk of predators.  That is why Jesus has come to be “the good shepherd” - to bring His sheep back to safety.  

But although Israel was intended to be an example to the world of how to live under God’s care, they wandered.  They gave little inspiration to the rest of the world to trust in God’s leadership.   Jesus said that His sheep (His people) were not just the spiritually lost people of Israel but everybody, Jews and Gentiles, who He would call into the eternal security of His kingdom.  God had promised that to Abraham two thousand years previously (Genesis 12:3).
 
Although the children of Israel, the descendants of Jacob ('Israel' was Jacob's God-given new name - Genesis 35:10) were special to God, Jesus said that people from every other nation also belonged to Him (Acts 18:10).  He promised to call them, and those who listened to His voice would come to Him and become one flock.  This was not a casual remark; He said that He 'must' bring them into His flock.  He was, and is, determined to extend His kingdom ... that is why He came to earth to die and open a way ... for 'whoever calls on His name to be saved' (Acts 2:21, Acts 4:12).  
 
Most people do not realise that God has 'ownership rights' over them.  He has created them, in His own image, and the sacrifice of Jesus is available to them ... if only they will hear His call.  But how will they hear?  Romans 10:14 says: "But how can they call on Him to save them unless they believe in Him? And how can they believe in Him if they have never heard about Him? And how can they hear about Him unless someone tells them?" (New Living Translation).  Some Christians think that means only 'qualified ministers' can tell others.  No!  If you know you have been saved by Jesus, you have enough information to tell others, and explain why you think and behave as you do.  And for many people those conversations happen most naturally with work colleagues who observe your way of life but cannot explain why (1 Peter 3:15-16).  Don't let them wander any further away from their Shepherd.  Just tell them about Jesus!