Portrait of a lady, with the Tiburtine Sibyl foretelling the advent of Christ to the emperor Augustus

Jan Mostaert's Portrait of a Lady with the Tiburtine Sibyl Foretelling demonstrates the Haarlem master's sophisticated engagement with the tradition of moralizing portraiture where the sitter is shown alongside a symbolic or historical figure relevant to their identity or situation. The Tiburtine Sibyl, who was said to have prophesied Christ's birth to Emperor Augustus, provided a learned classical frame for this otherwise conventional noble portrait. Mostaert's years at the Habsburg court under Margaret of Austria gave him access to the humanist intellectual culture that produced such learned iconographic programs for elite patrons.

The portrait is rendered with skilled technique characteristic of Jan Mostaert's best work. The tempera medium, applied in thin layers of egg-bound pigment over a prepared gesso ground, the subtle gradations of flesh tone and the textural contrasts between skin, fabric, and background that give the image its convincing presence.