That refers to the Judeo-Christian faith. Compare this fact with the elites of the major political party today, and the schools they oversee, teaching quite the reverse.
They also thought witchcraft was a thing.
That slavery was acceptable.
that bleeding someone was an valid treatment for Strep Throat.
We know all those things are ... you know... wrong now.
Of course, a lot of the Founders were Deists... but never mind.