Ok, it's a detail from the Procession of the Magi fresco in the Medici chapel in Florence, specifically part of the Procession of the youngest king. There's images of parts of it in the link above, or a full landscape here. Our chap is near the left end.

Benozzo Gozzoli, the artist, seems perfectly capable of painting hands, so it seems likely that he did this deliberately. He's included the likenesses of key members of the Medici family as the kings, and more of the family and their friends as the retinue, so it is very likely that the image represents a specific person. There's another figure, in the next panel, wearing a bright red cap, holding his hand in a similar way, so I suspect it is just supposed to show them relaxed, although the way the figure in the OP is holding his belt and staring at the viewer in an alnost challenging way makes me wonder if there is more the artist was trying to communicate.