“Live by the three (point shot), die by the three” is a basketball adage, borrowing its form from the older proverb “live by the sword, die by the sword.” Teams that rely too much on the three-point shot could run into a team that is expecting these shots and knows how to defend against them.
 
“But if you live by the three-pointer you can die by the three-pointer” has been cited in print since at least 1986, when it was said by Boston College Eagles basketball coach Jim O’Brien.
 
   
Wikipedia: Live by the sword, die by the sword
“Live by the sword, die by the sword” is a saying derived from a biblical parable to the effect that if you use violence, or other harsh means, against other people, you can expect to have those same means used against you; “You can expect to become a victim of whatever means you use to get what you want.”
 
The proverb comes from the Gospel of Matthew, verse 26:52, which describes a disciple (identified in the Gospel of John as Simon Peter) drawing a sword to defend against the arrest of Jesus in the Garden of Gethsemane, but is rebuked by Jesus, who tells him to sheath the weapon:
 
Then said Jesus unto him, Put up again thy sword into his place: for all they that take the sword shall perish with the sword (Matthew 26:52, King James Version)
 
29 November 1986, Boston (MA) Globe, “BC makes it a long night for Siena” by Barry Cadigan, pg. 22:
“But if you live by the three-pointer you can die by the three-pointer,” said O’Brien, who was able to regroup his Eagles, take a one-point lead out of the first half and stretch it to the game’s biggest lead, 10 points, at the end.
(Boston College Eagles basketball coach Jim O’Brien—ed.)
 
17 February 1988, The Interlake Spectator (Gimli, Manitoba), “Selkirk wins gold at Gimli games” by Terry Gavan, pg. 25, col. 1:
“If you live by the three pointer then you can die by the three pointer,” said Rutherford after the game.
(Stonewall guard Bruce Rutherford—ed.)
 
12 March 1994, Aberdeen (SD) American News, “West Central faces Lennox for State A title” (AP), pg. 2B, col. 5:
“You live by the three and you die by the three, but defense wins championships, and I think that what’s was the difference tonight,” said Lennox coach Tim Hooten.
 
Google Books
Larry Legend
By Mark Shaw
Lincolnwood, IL: Masters Press
1998
Pg. 240:
Live by the three, die by the three.
 
Google Books
Pete Newell’s Playing Big
By Pete Newell and Swen Nater
Champaign, IL: Human Kinetics
2008
Pg. 6:
Although the three-point shot is popular, we have seen enough teams that rely on the outside shot to agree with the saying, “Live by the three and die by the three.”
 
The Dream Shake (Houston Rockets Blog)
Rockets lose to the Lakers in OT, drop to 8th seed, will face OKC
By Jesus Acevedo Jr. on Apr 18 2013, 3:03a
(...)
There’s an old saying in basketball circles, “Live by the three, Die by the three”, and that was the Rockets undoing. One of the best three-point shooting teams in the league went 8-33 from behind the arc. A measly 24%. In the fourth quarter Houston only converted four three pointers. Hard to believe considering the Rockets made close to 900 three pointers in the regular season, their second highest total was in the 2006-07 season when they made 705. For the Rockets to surprise people and beat Oklahoma City they’re going to need to make three pointers.