Ephraim Hezekiah Bueno (1599-1665), or Bonus, was a prominent physician in Amsterdam and came from a Sephardic family of doctors. As a wealthy, literary man who both translated and wrote poetry he was a friend and supporter of Menasseh ben Israel, the theologian and publisher, and Rembrandt's neighbour on the Jodenbreestraat. It might well have been Menasseh who introduced Rembrandt to Bueno, thereby prompting the commission of this portrait.
Whilst most of his etched portraits were worked directly onto the plate, this etching is based on a small oil sketch, now in the Rijksmuseum. Although immediately recognisable, the etching is quite different from the sketch. While the little painting concentrates entirely on the doctor's features, in the etching Rembrandt added most of the body and all of the setting. More importantly however, he changed the expression of the sitter; in the sketch Bonus looks directly at us, in the print his right eye is diverted and seems to look into the middle distance. His stance at the foot of the staircase, hand resting on the banister, is quite formal and imposing, yet his distracted, introspective expression lends this portrait a sense of intimacy and melancholy.
Research into Rembrandt's papers has revealed that the first state (of which only four impressions are known) and the second state were printed practically at the same time, indicating perhaps that Rembrandt considered the first state unfinished. He completed the plate by adding some shading and burnishing the burr on Bueno's ring. No late impressions of this rare print are known, and although Hinterding distinguishes two editions 'the quality of these sheets is always so good that it is not easy to say which of the two editions is the earlier.' (Hinterding, p. 500)