And atte laste the feend, oure enemy,
Putte in his thought that he sholde poyson beye,
With which he myghte sleen his felawes tweye;
For-why the feend foond hym in swich lyvynge
That he hadde leve him to sorwe brynge.
For this was outrely his fulle entente,
To sleen hem bothe and nevere to repente.

– Geoffrey Chaucer

The Canterbury Tales, The Pardoner’s Tale. The youngest rioter is told by the Devil to buy poison with which to kill his two fellow rioters – he doesn’t want to share the gold find with them. The Devil is able to get into his thoughts because he already leads a sinful life and he has no intention of ever repenting, thus ensuring his damnation to hell.