I think this was covered in another thread, but it bears repeating here. Read what the people who wrote and signed the Constitution said about the subject, then decide for yourselves.

James Madison
" We've staked our future on our ability to follow the Ten Commandments with all of our heart."

"We have staked the whole future of American civilization, not upon the power of government, far from it. We've staked the future of all our political institutions upon our capacity…to sustain ourselves according to the Ten Commandments of God." [1778 to the General Assembly of the State of Virginia]

• I have sometimes thought there could not be a stronger testimony in favor of religion or against temporal enjoyments, even the most rational and manly, than for men who occupy the most honorable and gainful departments and [who] are rising in reputation and wealth, publicly to declare the unsatisfactoriness [of temportal enjoyments] by becoming fervent advocates in the cause of Christ; and I wish you may give in your evidence in this way.
Letter by Madison to William Bradford (September 25, 1773)
• In 1812, President Madison signed a federal bill which economically aided the Bible Society of Philadelphia in its goal of the mass distribution of the Bible.
" An Act for the relief of the Bible Society of Philadelphia" Approved February 2, 1813 by Congress

"It is the mutual duty of all to practice Christian forbearance, love, and charity toward each other."

• A watchful eye must be kept on ourselves lest, while we are building ideal monuments of renown and bliss here, we neglect to have our names enrolled in the Annals of Heaven. [Letter by Madison to William Bradford [urging him to make sure of his own salvation] November 9, 1772]

At the Constitutional Convention of 1787, James Madison proposed the plan to divide the central government into three branches. He discovered this model of government from the Perfect Governor, as he read Isaiah 33:22;
"For the LORD is our judge, the LORD is our lawgiver,
the LORD is our king;
He will save us."
[Baron Charles Montesquieu, wrote in 1748; "Nor is there liberty if the power of judging is not separated from legislative power and from executive power. If it [the power of judging] were joined to legislative power, the power over life and liberty of the citizens would be arbitrary, for the judge would be the legislature if it were joined to the executive power, the judge could have the force of an oppressor. All would be lost if the same … body of principal men … exercised these three powers." Madison claimed Isaiah 33:22 as the source of division of power in government