Jesus says His sheep follow Him because they know His voice. See John 10:2-5, 14-15.
“Note that Jesus did not say, ‘My prophets hear my voice.’ He didn’t say, ‘My pastors hear my voice.’ And he did not say, ‘Only the spiritual people hear my voice.’ But rather, ‘My sheep hear my voice.’ According to Jesus, his voice is not reserved for the spiritually elite, the priest, or the guru. Any ‘sheep’ can hear his call. That means you can hear it too!”
Brad Jersak, Can You Hear Me? Page 20
Note also that Jesus did not say “might hear,” “could hear,” “should hear,” or “would hear, if only…” “My sheep do hear my voice,” He asserts. It’s just a fact.