Browning hands his story to someone else to tell. The first stanza introduces "Grand rough old Martin Luther," who "Bloomed fables-flowers on furze," as if he took a prickly gorse bush and hung it with blossoms of invention. The rougher the man, the better the trick: "The better the uncouther." The stanza ends on a sly question, "Do roses stick like burrs?" A rose is pretty but doesn't cling, while a burr catches in your clothes and won't let go. The tale that follows is meant to be both, a flower with a hook in it.
The plot is simple. A beggar asks for alms at an abbey door. The abbot is "seized with qualms," a word that suggests a pang of conscience, yet he refuses anyway: "We're poor!" His excuse is revealing. The abbey "had plenty once, / When gifts fell thick as rain," and the abbot treats wealth as weather, something that happens to you, not something you do. "They give us nought, for the nonce, / And now should we give again?" The little phrase "for the nonce" makes his meanness sound like a reasonable, temporary pause.
The beggar answers with an allegory. He says the abbey once had two brothers as inmates, "Date and Dabitur." These are Latin words, "give" and "it shall be given," and they echo the biblical saying "Give, and it shall be given unto you." Instead of quoting the verse, the beggar turns it into two monks, and the abstract proverb becomes a household with a family problem. When Date was "in good case" (in good condition), Dabitur "flourished too." Now Dabitur has a "lenten face," lean as a Lent fast, and the beggar hints that Date has only himself to blame. The cure reverses the abbot's logic: "Try and make plump the other! / When Date's penance is done, / Dabitur helps his brother." The abbot waits to receive before he gives, and the beggar says the order is the wrong way round. Even the word "penance" treats stinginess as a spiritual debt to be worked off.
The form suits this teaching. The poem is built from quatrains with short, bouncing lines of roughly three beats, which gives it the feel of a folk tale or a rhyming proverb. The rhymes are part of the fun. "Luther" and "uncouther" make a comic double rhyme, and the beggar's "unless I err" is made to chime with "Dabitur," so the Latin name has to be stretched to fit. Browning seems to enjoy the clatter, and the roughness fits Luther's "uncouth" manner. The beggar's "ye" and "Of old" lend him an antique, preacherly voice, while the abbot's short, defensive exclamation sounds more like everyday excuse-making.
The ending is carefully unfinished. "Only, beware relapse!" is the beggar's parting warning, and "relapse" is a word for sliding back into sin or illness. It implies that generosity is a habit you can lose, not a single act you perform and have done with. The abbot "hung his head," but we never learn whether he opens his purse. Then Luther gives the verdict in a heavily hedged sentence: "This beggar might be perhaps / An angel." The stacked "might" and "perhaps" make the line stumble, and the rhythm falters just as the poem reaches its most solemn idea. Judging by the framing, the point is that wisdom has come from the doorstep and not from the abbey's inmates.
What makes the poem worth reading is how much argument it packs into so little space. It takes a familiar moral, that giving and receiving depend on each other, and turns it into a joke with characters, a plot and a sting. It also answers its own opening question. The fable sticks because it is a rose on a thorn bush: charming on the surface, with a barb underneath that catches the abbot, and the reader, who may have been thinking "We're poor!" too.