Voices are trustworthy and deeply personal, and since God made everything including us, he knows this. So does his Son Jesus, which is why he uses the metaphor of voice recognition of a loved one to describe the intimate bond he wishes to have with us his faithful. Jesus illustrates the bond in the case of a sheep recognizing the voice of his shepherd, but it’s actually baked into the entire animal world. For example, maybe you’ve seen nature videos where there are like 1000 identical baby birds or penguins bunched up and chirping, and yet a mother bird instantly recognizes her baby’s cry and feeds him.  The experiment I mentioned proves that this upper power is also baked into human family relations, but Jesus takes it a step further. He says our voice recognition of a loved one here on Earth is just a shadow of the intimate bond we can have as sons and daughters of the heavenly Father.