The Reformation produced an enormous amount of pamphlet writing, dense with citation and counter citation, arguing over how a person is saved. Lucas Cranach the Elder's Law and Gospel takes a different approach to the same argument: instead of paragraphs, a single panel split visually in half, with a dead tree and condemned figures on one side and a living tree with Christ's resurrection on the other.
Cranach painted the panel around 1529, probably with input from his own close friend Martin Luther, and it functioned as what art historians call a Merkbild, literally a memory picture, built specifically so a viewer who could not read Latin or follow a theological argument in prose could still grasp the doctrine at a glance. Law, on the left, shows the Old Covenant's demands and humanity's inability to meet them on its own. Gospel, on the right, shows salvation arriving as an unconditional gift through Christ rather than something earned.
The composition worked well enough that it did not stay confined to paint. Cranach's own workshop produced a related version now in Prague and a later one with his son in 1536, and other artists, Hans Holbein the Younger and Erhard Altdorfer among them, adapted the same left right structure into prints, relief carvings and household objects. A theological argument about grace ended up circulating, in visual shorthand, well beyond anyone who ever read a page of the pamphlets making the same case in words.