Ambrose of Milan’s hymn, ‘Splendor paternae gloriae’, uses metaphors of the sun and light to invoke the Trinity and invite God’s sanctifying work. Ambrose’s depiction of the Godhead in terms of the sun and its light demonstrates his careful engagement with traditional Christian metaphors, traditions which he carefully rearranges to align with his view of the Trinity. His representation of God’s sanctifying activity illustrates the Trinity’s inseparable operations, a central focus of his pro-Nicene works. These features suggest that Ambrose intended this hymn to serve as a confessio Trinitatis, perhaps amid the bishop’s conflicts with anti-Nicene factions in Milan.