Whan Costantyn of curteisie Holy Kirke dowed
With londes and ledes, lordshipes and rentes,
An aungel men herden an heigh at Rome crye,
"Dos ecclesie this day hath ydronke venym,
And tho that han Petres power arn apoisoned alle!"
Source, in full
When Constantine out of generosity endowed the Church / With lands and subjects, estates and rents, / Men heard an angel cry high above Rome, / "This day the true wealth of the Church has drunk venom / And those who have Peter's power are all poisoned."
Notes from Wikiquote
B-text, Passus 15, line 555 | Pietro Cali, Allegory and Vision in Dante and Langland (Cork UP, 1971) p. 150