The words of the exorcism spell, which the humans will have to say out loud in order to send the demon back to hell goes like this:
Exorcizamus te, omnis immundus spiritus, omnis satanica potestas, omnis incursio infernalis adversarii, omnis legio, omnis congregatio et secta diabolica...
Ergo, draco maledicte et omnis legio diabolica, adjuramus te ... cessa decipere humanas creaturas, eisque æternæ perditionìs venenum propinare...
Vade, satana, inventor et magister omnis fallaciæ, hostis humanæ salutis...
Humiliare sub potenti manu Dei; contremisce et effuge, invocato a nobis sancto et terribili nomine... quem inferi tremunt...
Ab insidiis diaboli, libera nos, Domine.
Ut Ecclesiam tuam secura tibi facias libertate servire, te rogamus, audi nos.
It is in latin, and if anyone was wondering, here is the translated text:
"We drive you from us, whoever you may be, unclean spirits, all satanic powers, all infernal invaders, all wicked legions, assemblies and sects...
... Thus, cursed dragon, and you, diabolical legions, we adjure you... stop deceiving human creatures and pouring out to them the poison of eternal damnation...
Be gone, Satan, inventor and master of all deceit, enemy of man's salvation...
Stoop beneath the all-powerful Hand of God; tremble and flee when we invoke the Holy and terrible Name... which causes hell to tremble...
From the snares of the devil, Deliver us, O Lord. That Thy Church may serve Thee in peace and liberty, We beseech Thee to hear us."
This exorcism spell is taken from the TV series Supernatural.