I think taking birth control precautions is pretty comission-y.
I must concur. We've been judging the wasting of sperm as an act of commission at least as far back as when Genesis was written.
Onan knew that the offspring would not be his; so when he went in to his brother’s wife, he wasted his seed on the ground in order not to give offspring to his brother. But what he did was displeasing in the sight of the LORD; so He took his life also.
Apparently that sperm really was sacred.
There's a little debate on what Onan was being punished for, whether it was the not-impregnating-and-disobeying-the-Lord or the spilling-seed part. I incline to the disobedience explanation; as the Wikipedia entry mentions, Leviciticus's punishment for spilling seeds is very far from 'execution'.
A few years ago, I wrote a little dialogue I imagined between 2 materialists, one of whom was for and one against abortion, centering on the personal identity question. I recently cleaned it up and added a number of references for the biological claims.
You can read it at An Abortion Dialogue.
Early feedback from #lesswrong is that it's a 'nicely enjoyable read' and 'quite good'. I hope everyone likes it, even if it doesn't exactly break new philosophical ground.