Vincent's NT Word Studies
5. When he hath found it. Matthew, If so be that he find it.On his shoulders. Lit., his own shoulders. "He might have employed a servant's aid, but love and joy make the labor sweet to himself" (Bengel). the "Good Shepherd" is a favorite subject in early Christian art. "We cannot go through any part of the catacombs, or turn over the pages of any collection of ancient Christian monuments, without coming across it again and again. We know from Tertullian that it was often designed upon chalices. We find it ourselves painted in fresco upon the roofs and walls of the sepulchral chambers; rudely scratched upon gravestones, or more carefully sculptured on sarcophagi; traced in gold upon glass, molded on lamps, engraved on rings; and, in a word, represented on every species of Christian monument that has come down to us.... It was selected because it expressed the whole sum and substance of the Christian dispensation.... He is sometimes represented alone with his flock; at other times accompanied by his apostles, each attended by one or more sheep.
Sometimes he stands amidst many sheep; sometimes he caresses one only; but most commonly - so commonly as almost to form a rule to which other scenes might be considered the exceptions - he bears a lost sheep, or even a goat, upon his shoulders" (Northcote and Brownlow, "Roma Sotteranea"). A beautiful specimen is found in the mausoleum of Galla Placidia, at Ravenna, erected about 450 A.D. It is a mosaic in green and gold. The figure is a beautiful one, youthful in face and form, as is usual in the early mosaics, and surrounded by his sheep. Facing this appears, over the altar, the form of Christ seated beside a kind of furnace, on the other side of which stands a little open bookcase. He is engaged in casting heretical books into the fire. Are they, indeed, the same - the Shepherd Christ of the Gospels, and the polemic Christ of the ecclesiastics?
Robertson's NT Word Studies
15:5 {On his shoulders} (epi tous wmous autou). He does it himself in exuberant affection and of necessity as the poor lost sheep is helpless. Note the plural shoulders showing that the sheep was just back of the shepherd's neck and drawn around by both hands. The word for shoulder (wmos) is old and common, but in the N.T. only here and #Mt 23:4. {Rejoicing} (cairwn). "There is no reproaching of the wandering sheep, nor murmuring at the trouble" (Plummer).