What happened

HSBC Holdings (NYSE:HSBC), the largest European bank and one of the largest financial institutions in the entire world, was having a tremendous day on Monday. While the S&P 500 was nearly 2% higher for the day as of 2:20 p.m. EDT and the Financial Select Sector SPDR ETF was up by about 3%, HSBC posted a double-digit gain, with shares climbing by more than 10% for the day.

So what

Today's move can be attributed to institutional buying.

Specifically, the bank's largest shareholder -- Chinese-based Ping An Insurance Group -- bought another 10.8 million shares of HBSC, which increases its stake in the bank to about 8% of the outstanding shares. This makes Ping An's investment worth about $6.5 billion after today's move.

Man looking at laptop with hand raised triumphantly.

Image source: Getty Images.

According to a Ping An spokesperson, the insurance company finds the current share price appealing, and thinks the bank's dividend suspension is merely a short-term issue.

Now what

This was HSBC's largest one-day rally since 2009, but it's important to realize that HBSC had been trading for just over a 25-year low and is still more than 50% below its 52-week high, so there's still a long way to go before most of the bank's investors will be back to even. However, it's certainly an encouraging sign that the bank's largest shareholder is willing to risk billions more on the bank's turnaround potential, especially since Ping An is already sitting on a loss of more than $8 billion on its HSBC investment.