In this painting, John the Baptist has summoned the multitudes to hear his message of repentance and salvation through baptism. Seated in the left foreground beside the sacrificial lamb, he wears the traditional, roughly cut pelt that is his attribute, and holds a reed cross. A thin banner winding around the cross bears the letters…ECC…AGN…a reference to the words John uttered when he saw Christ: “Behold the Lamb of God, behold him who taketh away the sins of the world” (Ecce agnus Dei, qui tollit peccatum mundi) (John 1:29). Under Reuter’s brush, this painting is not only an image of John preaching in the wilderness. It is also a psychological study of the crowd gathered around him. Reuter carefully individualizes the figures and their reactions. While many listen attentively with hands up in agreement or pressed to their faces in contemplation, others seem more reticent, such as the young girl in the center whose arms cross in front of her chest, evidently weary of John’s sermon.

The excellent preservation of the painting allows one to appreciate the great care with which the artist rendered the figures. He carefully blended tones and colors to achieve the enamel-like surface of the figures’ skin and clothing, and used a more open touch in the rendering of the landscape and foliage to enliven the scenes. Reuter may have learned this technique from Michael Sweerts (1618–1664), with whom he studied in Brussels in the late 1650s before moving to Rome in the mid-1660s. Reflections of Sweerts’s work is seen also in Reuter’s classicized, sculptural figures as well as in the rendering of light, which is both highly focused yet derived from a barely definable source. None of Reuter’s paintings are dated, but it seems probable that he created the Gallery’s painting in Brussels when he was still highly influenced by Sweerts.