A discussion of early church services in the House of Representatives appears on pages 84-97 of Religion and the Founding of the American Republic by James H. Hutson (Washington, D.C.: Library of Congress, 1998). The book is a catalog for an exhibition of the same title that was shown at the Library in the summer of 1998. An electronic copy of the book is available through the HathiTrust website at http://catalog.hathitrust.org/Record/003263301 , and an online version of the exhibit is at http://www.loc.gov/exhibits/religion/ .
The catalog cites a February 1801 letter from Senate Chaplain Thomas Claggett as a source for dating House services in the fall of 1800 (Claggett to James Kemp, 18 February 1801, Maryland Diocesan Archives).
The journals of the House and Senate can be read through the Library’s American Memory presentation “A Century of Lawmaking for a New Nation” website at http://memory.loc.gov/ammem/amlaw/lawhome.html . I note that Thomas Claggett was appointed “Chaplain to Congress” on November 27, 1800. In a brief look I didn’t see any references to Sunday services, but such events may not have been recorded as official legislative business.
References to Sunday services in the Capitol might be found in local DC newspapers such as The National Intelligencer and Washington Advertiser, which began publication on 31 October 1800. An online version can be viewed through the Library’s “Chronicling America” website at https://chroniclingamerica.loc.gov/lccn/sn83045242/ .
We hope that this information is useful.
Library of Congress