'Prevented' in the Bible

Sarai said to Abram, “Since the Lord has prevented me from bearing children, go to my slave; perhaps through her I can build a family.” And Abram agreed to what Sarai said.

Onan knew that the child (heir) would not be his [but his dead brother’s]; so whenever he lay with his brother’s widow, he spilled his seed on the ground [to prevent conception], so that he would not give a child to his brother.