WASHINGTON — When his pregnant wife first challenged circumcising their son, Mike Wallach had a gut reaction: “That’s what we do, we’re Jews!” But doubts about whether the surgery was medically necessary and concern over his wife’s opposition forced Wallach to confront some questions.

Can you be Jewish without Judaism’s oldest ritual? he says he asked himself. What does it mean to be Jewish?

Speaking with God, the 37-year-old screenwriter and grandson of Holocaust survivors explained he was using the “free will and brain you gave me” to reject circumcision. God, he concluded, wouldn’t be impressed by the desire to do something simply “for tradition’s sake.”

“I wasn’t at peace until I had that conversation,” said Wallach, who grew up in Northwest Washington and now lives in Brooklyn.

Wallach is among a small but growing number of Jews who are slowly altering what has for millennia been considered perhaps Judaism’s core rite. The Bible says an adult Abraham circumcised himself to mark the covenant between he and his descendants and God. Any male who doesn’t circumcise, God says in Genesis “that soul will be cut off from its people; he has broken My covenant.”