2 Samuel 13:13

Thee. Was she ignorant that such marriages could not be allowed? (Calmet) --- Some think she was. (Grotius) (Menochius) --- Others believe that, in her present situation, she said what first came into her head, to get out of the hands of her brother. The Rabbins pretend that she was conceived before David married her mother, and that the latter was a pagan; so that they suppose there was no relationship between Thamar and Amnon. But this is all asserted without proof. (Calmet)