Arguments over same-sex marriage played out in the U.S. Supreme Courton Tuesday, but many religious groups opposed to gay marriage aren’t waiting for a ruling. A court ruling expected two months from now could sanction same-sex marriage nationwide. In anticipation, some congregations and religious advocacy groups are re-emphasizing their teachings on marriage, fine-tuning their approach to gays and lesbians and bracing for legal battles and public criticism. “The outcome of this decision will shape the landscape of the church’s ministry in the U.S. for generations to come,” wrote Russell Moore, president of the Ethics & Religious Liberty Commission of the...