Franklin Graham, the son of evangelist Billy Graham and head of the Billy Graham Evangelist Association, warned Tuesday that allowing gay couples to marry will lead to “the disintegration of our culture.”

The Supreme Court will rule this month in a case challenging bans on gay marriage in four states. The ruling could strike down the nation's remaining 13 bans, leading to nationwide marriage equality.

“This is a pivotal moment in the history of our nation,” Graham wrote in a Charisma News op-ed. “If the nation's highest court decrees same-sex marriage as the law of the land, the consequences will be grave. It sets the stage for persecution of believers who are committed to the truth of Scripture,” Graham wrote.

“The ultimate danger, of course, is the devastating results of disobedience to God's Word. Continual blatant sexual immorality that shakes its arrogant, godless fist before Almighty God is a flashing red sign warning of the imminent disintegration of a culture,” he added.

On Facebook, Graham has been actively calling on followers to pray for each justice to vote the way Graham believes God wants them to.

“As the Supreme Court continues to deliberate over the constitutionality of same-sex marriage, let's pray that Justice Ginsburg's eyes would be opened to the truth of Scripture and that she would not be deceived by the arguments of those who seek to impose their 'new morality' on our nation,” Graham wrote of Justice Ruth Bader Ginsburg, who is Jewish.

“Today join me in praying that Justice [Samuel] Alito will have wisdom and stand strong for what we know is God's unchanging truth – Marriage is between 1 man and 1 woman,” he wrote in a separate post.

(Related: Franklin Graham prepared to have his head “chopped off” for opposing gay rights.)