Joseph William Martin, Jr. (1884-1968) was a Republican Minority Leader in Congress in 1946; after Republicans won the November 1946 elections, Martin became the House Speaker. In February 1946, Martin said: “If the Republicans win control of this body next November, we will open each session with prayer and close it with a probe.”
 
The 80th Congress didn’t always “open with a prayer and close with a probe,” but the new House majority of Republicans did make several probes of Democrats.
       
 
Wikipedia: Joseph William Martin, Jr.   
Joseph William Martin, Jr. (November 3, 1884 - March 6, 1968) was a Republican Congressman and Speaker of the House from North Attleborough, Massachusetts. He was notably the only Republican to serve as Speaker from 1931 until 1995.
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Leadership
He served as Speaker of the House of Representatives on two separate occasions from 1947 to 1949 and from 1953 to 1955. These terms represented two Republican short-term majorities in the House, and Martin’s two terms were bookended by Sam Rayburn (D-TX).
 
Following dramatic Republican losses in the 1958 election cycle, which placed a return to majority status out of reach (for 36 more years, as it turned out, until the 1994 Republican Revolution), Martin was ousted from the leadership by Charles A. Halleck of Indiana. In spite of this defeat, Martin chose to remain as a backbench member of the House. Eight years later, in 1966, he was ousted from his seat in the Republican primary by Margaret Heckler, who was 46 years his junior.
 
Office of the Chaplain
History of the Chaplaincy
Article I, Section 2 of the Constitution states: “The House of Representatives shall chuse their Speaker and other Officers.”
 
The election of the Rev. William Linn as Chaplain of the House on May 1, 1789, continued the tradition established by the Continental Congresses of each day’s proceedings opening with a prayer by a chaplain. The early chaplains alternated duties with their Senate counterparts on a weekly basis. The two conducted Sunday services for the Washington community in the House Chamber every other week.
 
Since the election of Rev. Linn in 1789, the House has been served by chaplains of various religious denominations, including Baptist (7), Christian (1), Congregationalist (2), Disciples of Christ (1), Episcopalian (4), Lutheran (1), Methodist (16), Presbyterian (15), Roman Catholic (1), Unitarian (2), and Universalist (1).
 
In addition to opening proceedings with prayer, the Chaplain provides pastoral counseling to the House community, coordinates the scheduling of guest chaplains, and arranges memorial services for the House and its staff. In the past, Chaplains have performed marriage and funeral ceremonies for House members.
     
5 February 1946, Port Arthur (TX) News, “National Whirligig” by Ray Tucker, pg. 4, col. 5:
“Open With Prayer, Close WIth Probe”
House Minority Leader Joseph W. Martin, Jr., of Massachusetts has warned Democratic colleagues that “If the Republicans win control of this body next November, we will open each session with prayer and close it with a probe.”
 
Google Books
1 April 1946, Life magazine, pg. 88, col. 2:
If the Republicans, to quote Joe Martin, ever get the chance to open each congressional day with a prayer and close it with a probe, there are those who confidently predict that Homer Ferguson will wind up with an investigator’s reputation to challenge that achieved by Hugo Black or the late Tim Walsh.
 
Google News Archive
28 September 1946, Pittsburgh (PA) Post-Gazette, “Republican Women See Radical Element Invading Schools” by Ingrid Jewell, pg. 3, col. 2:
Prayer and Probe
Representative Charles Hallock of Indiana, chairman of the Republican Congressional Committee, went further, and said if the Republicans carry the House, “every session will open with a prayer and close with a probe.”
   
Google News Archive
7 December 1946, Nashue (NH) Telegraph, “National Whirligig” by Ray Turner, pg. 4, col. 3:
DELAY—The immenence of Republican control of Congress has temporarily stalled the operation of the executive machinery at Washington and delayed presidential action on many important domestic and foregin problems.
 
Remembering “Speaker” Joseph W. Martin Jr.‘s pledge to “open each session with a prayer and end it with a probe,” President Truman aims to restrict the field of hostile investigation by postponing settlement of numerous high controversial issues.
     
14 December 1946, Oregonian (Portland, OR), “messages Not provocative of Party Strife” by Doris Fleeson, pg. 6, col. 3:
The Republicans are also moving closer to the good housekeeping conception for the next session. The prayer-probe-and-pass-the-tax-reduction mood with which they hailed their victory has passed. All their real leaders now appear resigned to long sessions over the budget before they dally with taxes.
 
Google News Archive
7 June 1947, St. Petersburg (FL) Times, “Washington Merry-Go-Round” by Drew Pearson, pg. 6, col. 5:
MINOR MYSTERIES—(...) What happened to Ohio Congressman Clarence Brown’s threat to open each session of the 80th Congress “with a prayer and close with a probe?”
   
Google News Archive
27 July 1947, Pittsburgh (PA) Press, “GOP Congress Votes Probe of High Prices in Drive to Adjourn,” pg. 1, col. 2:
The Republicans promised in advance to open every session of the 80th Congress with a prayer and close it with a probe.
 
There weren’t quite that many investigations, but there were a lot, with more to come.
       
Google Books
Harry Truman, President
By Frank McNaughton and Walter Hehmeyer
New York, NY: Whittlesey House
1948
Pg. 169:
An ebullient Republican prediction that the Congress would daily “open with a prayer and close with a probe” was quickly forgotten. The country had not voted for a post-mortem or for grand-jury proceedings.
 
8 September 1963, Chicago (IL) Tribune, “Next Crime Probe May Surpass 1950-1951 Hearing”:
At one time it was said that sessions of Congress opened with a prayer and closed with a probe.
 
9 November 2006. San Diego (CA) Union, “Election gives Bush, Democrats second chance”:
In 1946, Republican Speaker Joe Martin famously promised “to open every session with a prayer and close with a probe” of Truman.