This is a detail from an Ethiopian diptych of the life of the Virgin Mary, from the Annunciation to her Dormition (Assumption).
Mary, who is seated on a three-legged stool, is busily at work making thread. Gabriel appears at her right side with the message, while the Holy Spirit comes down in a white cloud. On the other side (Mary's upraised arm creating a nice division between two scenes), we find the very next story in the Gospel narrative, with Mary visiting her kinswoman Elizabeth.
As is traditional in Eastern icons, Mary is wearing a red dress, symbolic of her human nature, while she is enfolded in heavenly grace (blue).
See the full two-page spread from the 17th century in great detail at the website of the National Museum of African Art.