Years ago in a church I served previously, there was a farmer who owned some sheep. He told me one Sunday morning while we were on the subject of these verses from John's Gospel that every night when he pulled into his driveway with his big Ford pickup, those sheep could tell that it was his truck and they started making a racket because they knew it was feeding time. If there was an evening when he was late, and his wife would arrive home before him in her car, the sheep would stay quiet. They were never confused as to the sound of her car and his truck. When he arrived home, the sheep knew the sound of his truck.
Sheep not only get to know the sound of the vehicle the shepherd drives, but they get to know the sound of his voice. This is because the shepherd is always around. Sheep are not very bright animals, so it may take some time, but they do recognize the shepherd's voice. Jesus contrasts the loyal shepherd with the hired ranch hand who has no interest in the sheep, other than he needs to watch them to make money, which is only what is of concern. But when real danger approaches, the hand flees leaving the sheep vulnerable. The hand cares more about himself than his charge. The sheep cannot know the ranch hand's voice because he doesn't stick around long enough for them to hear it. Loyal and committed shepherds in first century Israel, however, had a dangerous job. William Loader writes,
The ancient shepherd of Palestine or Asia Minor had to be tough, worked often in areas of sparse growth, frequently amid danger from wild animals and sheep stealers, and, above all, had to protect the flock, especially at night, when they would often be rounded up into a small pen. John 10 reflects this less than idyllic world. The bland teddy bear image gives way to a picture of tension: positively, a shepherd doing his job to the utmost; negatively, dangers which threaten the sheep (in the present and the future) and which will kill him. Life and death dance together.Jesus proclaims himself as the good shepherd, and a necessary quality of a shepherd that is good is that he is loyal to the sheep. The prophets Jeremiah and Ezekiel criticized Israel's leaders for being bad shepherds to the people (Jeremiah 23:1; Ezekiel 34:7-11), allowing them to be scattered on account of their greed and disobedience. It should be noted in Ezekiel 34:11, God says, "I myself will search for my sheep, and will seek them out. If the "I am" sayings in John's Gospel are meant to be revelatory of Jesus' divinity, Jesus' claim to be the good shepherd may be a divine connection to the God in Ezekiel who declares himself to be shepherd of the people.
The reason the sheep know the shepherd's voice is because the shepherd is always there speaking to the sheep and protecting them from danger. The good shepherd is the loyal shepherd who is willing to die for the sheep in order to keep them safe.
In Jesus, the shepherd's crook takes a cruciform shape