“Never walk the leadoff hitter” (baseball adage)

“Never walk the leadoff hitter/man” is an old baseball adage. You don’t give the batter a free pass to first base—rather, throw a strike and give the fielders an opportunity to make a play on the ball.
 
“Never walk the leadoff man, especially in extra innings” was cited in 1965. “You don’t walk the leadoff man. You try to pitch him low and outside” was cited in 1967. “The cardinal rule of baseball: never walk the lead off man to start the inning” was cited in 1974. “One of baseball’s sacred commandments: Thou shalt not walk the leadoff hitter” was cited in 1986.
 
 
21 June 1965, The Daily Courier (Connellsville, PA), “S. Connellsville, Elks Are Winners,” pg. 7, col. 3:
The Lions learned an old baseball lesson all over again—never walk the leadoff man, especially in extra innings.
 
6 October 1967, The Plain Dealer (Cleveland, OH), “How About That Yaz Jazz?” by Hal Lebovitz, pg. 51, col. 4:
You don’t walk the leadoff man. You try to pitch him low and outside.
 
16 July 1972, Markham (IL) Star Tribune, “Harvey Bows Out” by Dennis Mahoney, pt. 2, pg. 17, col. 6:
Rich compounded his problems by violating a basic rule for pitchers, namely never walk the leadoff hitter.
 
15 August 1974, Park Forest (IL) South Star, “Matteson Gets By Hazel Crest” by Tom Gardiner, pg. D-1, col. 6:
The cardinal rule of baseball: never walk the lead off man to start the inning was broken by Browne to start the third.
 
Google News Archive
11 October 1986, Pittsburgh (PA) Post-Gazette, “Angels edge Red Sox, 5-3; lead series, 2-1” by Bruce Keidan, pg. 19, col. 4:
It happened in part because he violated one of baseball’s sacred commandments: Thou shalt not walk the leadoff hitter.
 
Google News Archive
29 June 1987, Gettysburg (PA) Times, “Cangelosi plays big role as Pirates trim Chicago” (AP), pg. 3B, col. 1:
“It’s always bad when you walk the leadoff hitter but it’s magnified when it occurs in the late innings,” (Chicago Cubs pitcher Rick—ed.) Sutcliffe said.
   
Google Books
Pitching
By Dan Schlossberg
New York, NY: Little Simon
1991
Pg. 47: 
OREL HERSHISER
Never walk the leadoff batter. He’ll score 80 percent of the time.
 
Twitter
Braves Lee
‏@braveslee
Thou shalt not walk the leadoff man.
9:03 PM - 6 May 2015
 
CLNS Radio
Friday, 08 May 2015 22:27
Boston Red Sox: Blue Jays Shut Out Hapless Sox 7-0
Written by Bob Snowdon
(...)
Miley had another rough stretch in the 6th when he walked Edwin Encarnacion to open the inning (old adage: Never walk the lead-off hitter), Russell Martin followed with a soft single to left and Encarnacion came home when Danny Velencia singled to center, with Martin moving to third.