Isaiah 30
19 You will live in Zion, in Jerusalem. You won’t cry anymore. Yahweh will certainly have pity on you when you cry for help. As soon as he hears you, he will answer you. 20 Adonay may give you troubles and hardships. But your teacher will no longer be hidden from you. You will see your teacher with your own eyes. 21 You will hear a voice behind you saying, “This is the way. Follow it, whether it turns to the right or to the left.” 22 Then you will dishonor your silver-plated idols and your gold-covered statues. You will throw them away like clothing ruined by stains. You will say to them, “Get out!”

We will know his voice when he speaks to us.

John 10:27-28
27 My sheep hear my voice, and I know them, and they follow me: 28 And I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand.