"I am going to call the priest."
Translation:Voy a llamar al sacerdote.
"Priest" is the direct object of this sentence. When the DO is a person or a pet, an untranslated "personal a" is used before it.
Veo a mi papá. I see my dad.
Ama a su esposa. He loves his wife.
¿Oyes a tu perro? Do you hear your dog?
In Dúo's sentence, the personal a combines with the el to form al.