It is properly used as a transitive verb, but in conversation is very often used intransitively.
"A Collection of College Words and Customs"
Benjamin Homer Hall
2. intransitively, to rehearse a lesson.
"A Collection of College Words and Customs"
Benjamin Homer Hall
If we speak of feeling any mental affection, or if we use the verb intransitively, the infinitive that follows, requires the preposition; as, "I feel it to be my duty."
"The Grammar of English Grammars"
Goold Brown