What does Luke 15:4 mean?

Religious leaders are condemning Jesus' decision to engage people they deem "too sinful" to even acknowledge. Jesus responds with three parables that show how God longs to reconcile with those who need Him most (Luke 15:1–3). Jesus begins here with the parable of the lost sheep. Jesus frames the parable to put the listener in the role of the main character. You are a shepherd. You have ninety-nine sheep. One of them wanders off, which is unwise, unsafe, and irrational. Roaming away from protection and safety is "stupid," in the sense of being a terrible choice. Still, what would a shepherd do about such a sheep?

This challenge has historical significance. The Pharisees are religious leaders. While not as official as priests, they are more familiar to the people and more easily respected. Practically speaking, they are the primary spiritual leaders of the people; they are the "shepherds" of that "flock." But Jewish spiritual shepherds do not have a good track record. In Ezekiel 34, God strongly condemns religious leaders who abuse, take advantage of, and abandon God's people (Ezekiel 34:1–5). He specifically says, "My sheep were scattered; they wandered over all the mountains and on every high hill. My sheep were scattered over all the face of the earth, with none to search or seek for them" (Ezekiel 34:5–6).

Jesus is challenging the Pharisees to see themselves as they really are. They have abused and abandoned the people by burdening them with laws God did not give them and then refusing to help them fulfill those laws (Luke 11:46). Instead, they should emulate God and actively seek out and rescue the foolish. The Pharisees should welcome the sinners and tax collectors and invite them to meals. Spiritually, sinners are the "poor, the crippled, the lame, the blind" (Luke 14:13) and the Pharisees will be blessed by God for feeding those who cannot repay (Luke 14:14).