God the Father doesn’t explicitly mention abortion in scripture and explain that its wrong, meaning you will not find the word “abortion” as banned in Deuteronomy or anywhere else. Neither does Jesus in the Gospels, or any other New Testament writer.
Catholic teachings against abortion are based on those against killing. A frequent Catholic response is that abortion is always wrong because God is always against the destruction of human life, based on the Ten Commandments. Another frequent argument is that God knows all humans before they were born, so God would never want human life ended before birth (this idea is based on the passage where God says he knew Isaiah would be his prophet before he was born). But God the Father frequently ordered killing in the Bible, including criminal executions and offensive war. God specifically demanded the killing of children and pregnant women when he commanded that defeated enemy nations be eliminated. According to scripture, God did not see these killings as immoral murder. Revelation states that Jesus will personally lead armies and kill God’s enemies. I’ve met a few Catholics who are against abortion on sanctity of life grounds, and who also believe that its always wrong to take human life. But I think most Catholics approve of police deadly force when need, or just wars as the Church teaches, even if it that means that millions of civilians will die, including pregnant women and children, like in the world wars. My point is not to criticize the Church or scripture here, but to point out how people look at killing in different ways.
When people say that abortion is wrong because God is always against killing, or always against the killing of babies, most of them mean that God is always against intentionally killing babies in the specific context of abortion. The frequent objection to this is that it means that once a female has become pregnant, God would require her to give birth even in what would normally be repugnant and harmful circumstances. So this would mean that God would always insist that a raped woman have her rapist’s child, to the point of avoiding post-rape contraception to make sure its not prevented, or that God would always insist that a minor have a child, or that a sick woman have a child even if it would endanger her life. Many Catholics will often argue that abortion is always more emotionally harmful than giving birth, but human emotions are subjective - what we are talking about here is why God himself would always forbid abortion. Sometimes Catholics will interpret scripture as saying that a woman’s body is not her own, but that its simply used as a breeding vessel when God wants to create new life. This idea assumes that its always God’s will (not just his permissive will, but his personal agency) when a woman becomes pregnant, and so this means that it would also have been God’s will for a woman to have been raped, or a minor child to have had underage sex, or for a woman to be endangered by a pregnancy. An objection to the idea of rape and underage pregnancy as being God’s will is the fact that in scripture, God forbids both rape and unmarried sexual activity.
Another frequent argument for abortion always being wrong is the idea that any impregnated woman has an obligation to give birth, because she received the benefit of a womb herself. This argument states that its unfair for anyone who has been born themselves to support abortion under any circumstances. I mention it here because its often linked to the idea that its always God’s will for a woman’s body to be used for reproduction, and for a child to be carried to term, once a woman has become pregnant.
