Projected number one overall pick Joe Burrow's hand size "was tied for the smallest among first-round quarterbacks measured at the combine since 2008"

Nine inches.

Here's a WaPo article from 2016 about obsession with hand size:

Disproving Jackson would be Minnesota Vikings quarterback Teddy Bridgewater, who had the smallest hands of all the quarterback prospects in the 2014 draft

...

As one would expect of someone who drafted the small-handed Bridgewater, Vikings General Manager Rick Spielman doesn’t think hand size matters all that much.

“A guy could have tiny Burger King hands, and — we’ll track him

...

This year’s small-hands winner/loser seems to be Arkansas quarterback Brandon Allen, whose hands were measured at 8 1/2 inches last month at the Senior Bowl. Feldman adds that Allen has been working twice a week with a masseuse to get his hands up to NFL par.

And from 2014:

From 1st Overall to Free-Falling: What Happened to Teddy Bridgewater?

...

Bridgewater blamed the poor showing on his decision not to wear gloves