Genesis 18 tells a specific story: three travellers visit Abraham at the oak of Mamre, he and his wife Sarah feed them, and one of the three turns out to speak with the authority of the Lord himself. Byzantine and early Russian icon painters had shown this scene for centuries as a hospitality narrative, with Abraham and Sarah serving the meal and the three angels seated at table. Andrei Rublev, working for the Trinity Cathedral at Sergius of Radonezh's monastery sometime in the 1420s, made one decision that changed what the image was.
He removed Abraham and Sarah entirely. What remains is three winged figures seated in an unbroken, gentle circle around a chalice holding a single sacrificed calf, their heads inclined toward each other in a rhythm that has no single centre and no hierarchy of size or position. A tree, a mountain and a building stand behind the three figures respectively, read since as symbols of life, of ascent, and of the church or household of God, though Rublev leaves no inscription explaining them.
By cutting the human hosts out of their own dinner, Rublev turned a story about hospitality into a picture with no subject except the three figures' relation to each other and to the viewer, who is left facing an open space at the table's fourth side. Byzantine theology had long read the three visitors as a hint of the Trinity hidden inside an Old Testament story; Rublev's composition made that hidden reading the icon's entire and only visible subject, which is why Russian tradition came to call the work simply Troitsa, the Trinity, rather than the Hospitality of Abraham.