The one reason you need to buy stocks right now

Stocks have been taking a beating over the past month—but one technical indicator suggests they could now be a buy.

"It's very similar to these oversold pullbacks we've had over the past few years," said Ari Wald, head of technical analysis at Oppenheimer & Co. "Oversold conditions are a reason to buy the market."

The S&P is down less than 3 percent from recent highs. But Wald says the market is already a buy on weakness.

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He looks to one indicator: The percentage of stocks above their 50-day moving average. In June, around 90 percent of stocks were above their 50-day moving average. Now, just 23 percent are, which is the lowest that reading has been since November 2012.

"As a sign of internal exhaustion, we view this as a buy signal," Wald wrote in a recent note.

Gina Sanchez, founder of Chantico Global, doesn't believe that stocks are trading at a discount despite indicators saying they are oversold.

"We're still not screamingly cheap yet," said Sanchez, a CNBC contributor. "We're right at about fair value now."

She expects that the S&P will keep falling, which "should take out what are the remaining market participants that are holding on."

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But her outlook for year-end is more constructive.

"Once we see that capitulation, I do actually think that we could see a recovery coming into the fall," she said.

To see the full discussion on the S&P 500, with Wald on the technicals and Sanchez on the fundamentals, watch the above video.

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