When the Pharisees and scribes complained that Jesus received sinners and ate with them, He told them a parable that we call the parable of the lost sheep (Luke 15:1-7).
“What man among you, if he has a hundred sheep and has lost one of them, does not leave the ninety-nine in the open pasture and go after the one which is lost until he finds it? “When he has found it, he lays it on his shoulders, rejoicing. “And when he comes home, he calls together his friends and his neighbors, saying to them, ‘Rejoice with me, for I have found my sheep which was lost!’ “I tell you that in the same way, there will be more joy in heaven over one sinner who repents than over ninety-nine righteous persons who need no repentance. (Luke 15:4-7 NAU)
“When he has found it, he lays it on his shoulder, rejoicing.” This describes the work of good shepherds and a practice that was well known to those who heard Jesus. On another occasion Jesus called Himself the good shepherd (John 10:11, 14).
The motif of the good shepherd with the sheep on his shoulder became common in later Christian iconography. Similar drawings are known from the catacombs in Rome. The four statuettes shown below date from the 4th century A.D., and are displayed in the Istanbul Archaeological Museum.
Last September I saw a special exhibit of early Christian artifacts in the Vatican Museum. The photo below shows a wonderful early 4th century statuette of the Good Shepherd.