The letter that President Lincoln sent to a Mrs Bixby of Boston during the Civil war strongly suggests otherwise:
Executive Mansion,
Washington, Nov. 21, 1864.
Dear Madam,
I have been shown in the files of the War Department a statement of the Adjutant General of Massachusetts that you are the mother of five sons who have died gloriously on the field of battle. I feel how weak and fruitless must be any word of mine which should attempt to beguile you from the grief of a loss so overwhelming. But I cannot refrain from tendering you the consolation that may be found in the thanks of the Republic they died to save. I pray that our Heavenly Father may assuage the anguish of your bereavement, and leave you only the cherished memory of the loved and lost, and the solemn pride that must be yours to have laid so costly a sacrifice upon the altar of freedom.
Yours, very sincerely and respectfully,
A. Lincoln
It’s not certain that Lincoln personally wrote the letter to Mrs. Bixby. Some think John Hay was the actual author. Mrs. Bixby had two sons killed in the war but apparently three survived the war. She is alleged to have been a Confederate sympathizer and a madam, and supposedly she destroyed the letter from Lincoln after receiving it. The fate of the original copy is unknown.
Abraham Lincoln (1809—1865. 16th President from 1861 to 1865; led his country through its greatest constitutional, military and moral crisis – the American Civil War – preserving the Union while ending slavery, and promoting economic and financial modernization) — It is the duty of nations, as well as of men, to own their dependence upon the overruling power of God and to recognize the sublime truth announced in the Holy Scriptures and proven by all history, that those nations only are blessed whose God is the Lord...
But we have forgotten God. We have forgotten the gracious Hand which preserved us in peace, and multiplied and enriched and strengthened us; and we have vainly imagined in the deceitfulness of our hearts, that all these blessings were produced be some superior wisdom and virtue of our own. Intoxicated with unbroken success, we have become too self-sufficient to feel the necessity of redeeming and preserving grace, too proud to pray to the God that made us!
It behooves us, then, to humble ourselves before the offended Power, to confess our national sins, and to pray for clemency and forgiveness.
Now, therefore, in compliance with the request, and fully concurring in the views of the Senate, I do, by this my proclamation, designate and set apart Thursday, the 30th day of April, 1863, as a day of national humiliation, fasting, and prayer. And I do hereby request all the People to abstain, on that day, from their ordinary secular pursuits, and to unite, at their several places of public worship and their respective homes, in keeping the day holy to the Lord, and devoted to the humble discharge of the religious duties proper to that solemn occasion.
All this being done, in sincerity and truth, let us then rest humbly in the hope, authorized by the Divine teachings, that the united cry of the Nation will be heard on high, and answered with blessings, no less the pardon of our national sins, and the restoration of our now divided and suffering Country, to its former happy condition of unity and peace. (Proclamation for National Day of Humiliation, Fasting, and Prayer; http://peacebyjesus.witnesstoday.org/ProclamationNationalFastDay.html)
• Intelligence, patriotism, Christianity, and a firm reliance on Him who has never yet forsaken this favored land, are still competent to adjust in the best way all our present difficulties. (A Compilation of the Messages and Papers of the Presidents, 1789-1897, James D. Richardson, editor [Published by Authority of Congress, 1899), Vol. VI, p. 11, from his First Inaugural, March 4, 1861])
• That every man may receive at least a moderate education, and thereby be enabled to read the histories of his own and other countries, by which he may duly appreciate the value of our free institutions, appears to be an object of vital importance, even on this account alone, to say nothing of the advantages and satisfaction to be derived from all being able to read the Scriptures, and other works both of a religious and moral nature for themselves. (The Collected Works of Abraham Lincoln, Roy P. Basler, editor [New Jersey: Rutgers University Press, 1953], Vol. I, p. 8, from his "Communication to the People of Sangamo County," March 9, 1832)
• [Attributed] As a ruler I doubt if any president has ever shown such trust in God, or in public documents so frequently referred to Divine aid. Often did he remark to friends and to delegations that his hope for our success rested in his conviction that God would bless our efforts, because we were trying to do right. To the address of a large religious body he replied, "Thanks be unto God, who, in our national trials, giveth us the Churches." To a minister who said he hoped the Lord was on our side, he replied that it gave him no concern whether the Lord was on our side or not "For," he added, "I know the Lord is always on the side of right;" and with deep feeling added, "But God is my witness that it is my constant anxiety and prayer that both myself and this nation should be on the Lord's side." (Rev. Matthew Simpson, D.D, May 4, 1865, Funeral address, Methodist Episcopal Church, Springfield, Illinois; http://beck.library.emory.edu/lincoln/sermon.php?id=simpson.001)