John 10:27 (ESV) … “My sheep hear my voice, and I know them, and they follow me.”
In this grand statement, Jesus summarized the blessings of those who truly listen to and believe the gospel. The believer in Jesus knows him personally, has eternal life, will not perish, and is secure in his care. But many of those who heard had no intention of truly listening. It is also true that those refusing to listen to Jesus’ voice are not his sheep. We recognize Christ’s voice when he speaks to us through the Bible. Are we truly listening for his voice? 
Those who belong to the Lord recognize his voice and respond to his word. That is the outward proof of inward faith.