A number of sources attribute a "National Prayer of Peace" to Thomas Jefferson. The text is as follows:
Almighty God, Who has given us this good land for our heritage; We humbly beseech Thee that we may always prove ourselves a people mindful of Thy favor and glad to do Thy will. Bless our land with honorable ministry, sound learning, and pure manners.
Save us from violence, discord, and confusion, from pride and arrogance, and from every evil way. Defend our liberties, and fashion into one united people the multitude brought hither out of many kindreds and tongues.
Endow with Thy spirit of wisdom those to whom in Thy Name we entrust the authority of government, that there may be justice and peace at home, and that through obedience to Thy law, we may show forth Thy praise among the nations of the earth.
In time of prosperity fill our hearts with thankfulness, and in the day of trouble, suffer not our trust in Thee to fail; all of which we ask through Jesus Christ our Lord, Amen.
We have no evidence that this prayer was written or delivered by Thomas Jefferson. It appears in the 1928 United States Book of Common Prayer, and was first suggested for inclusion in a report published in 1919.
Interestingly, although we can find no evidence that this prayer has a presidential source, it was used by a subsequent president in a public speech. Several months after his 1930 Thanksgiving Day Address as Governor of New York, it was pointed out that Franklin Delano Roosevelt's speech bore a striking resemblance to the very same prayer discussed above.
Ultimately, it seems unlikely that Jefferson would have composed or delivered a public prayer of this sort. He considered religion a private matter, and when asked to recommend a national day of fasting and prayer, replied, "I consider the government of the US. as interdicted by the constitution from intermedling with religious institutions, their doctrines, discipline, or exercises."
931 Thomas Jefferson Parkway
Charlottesville, VA 22902