Billionaire Warren Buffett's big bet on Apple is a telling sign for investors, closely followed trader Art Cashin told CNBC.
That's because the legendary investor stayed away from tech companies for a long time, saying he doesn't buy anything he can't understand, Cashin said.
"For him to double down on Apple, that's more of an all-clear signal than anybody's seen," the UBS director of floor operations at the New York Stock Exchange said on "Closing Bell."
Apple surged Friday after Buffet announced his Berkshire Hathaway bought 75 million shares in the first quarter. The stock closed at $183.83, a record high, and is now roughly $20 per share short of a $1 trillion market cap.
"The idea that you're going to spend loads of time trying to guess how many iPhone X ... are going to be sold in a three-month period totally misses the point," Buffett told CNBC's Becky Quick on Thursday evening just ahead of Berkshire Hathaway's annual shareholders meeting in Omaha, Nebraska.
"It's like worrying about the number of BlackBerrys 10 years ago," he added.
Apple's rally helped push the Dow Jones industrial average higher on Friday. The blue-chip index closed up 332.36 points at 24,262.51.
Meanwhile, the closed 1.3 percent higher to finish at 2,663.42 and the Nasdaq composite rose 1.7 percent to close at 7,209.62
Cashin expects the market to keep seesawing. On Thursday stocks saw big declines before turning around by the close. He called it a "minor trapdoor sell-off" that turned around after equities didn't cross the lower low.
"The game's not over. We're going to keep testing. This is kind of like someone who's had a minor heart attack and they want to know, 'how strong do I feel. Can I make it to the end of the block or after that?'" Cashin said.
"The market is basically taking its own pulse and its own temperature, testing these levels to see where they want to go," he added.
— CNBC's Thomas Franck and Sara Salinas contributed to this report.