Jason Kelce's taken a bizarre stance on X ... claiming he never washes his feet and people shouldn't trust "Big Soap" -- and, many are taking it as a shot at his bro's teammate.

The former Eagles center took to the popular social media site Saturday and engaged a troll who claims JK doesn't wash. Instead of letting the insult lie or firing back, Jason seemed to play into it, writing "What kind of weirdo washes their feet..."

It's a perfect way to handle a troll, ya gotta say ... agreeing with the joke to take its power away -- but, then the big man doubles down on his wisecrack.

Basically, Jason goes after "Big Soap" for hoodwinking people ... claiming hot spots are good for the health -- while soap and shampoo never did nothing for no one.

Basically, seems like JK's decided to go to war with X users in the most ridiculous, sarcastic way possible -- and, it's hilarious. No way the guy doesn't use soap after all ... he spent most of his life playing one of the sweatiest sports around.

But, fans are seeing a deeper meaning here ... 'cause many are pointing to Jason using the term "diabolical liars" as a shot at Harrison Butker.

During the kicker's controversial commencement speech, he said, "I want to speak directly to you briefly because I think it is you, the women, who have had the most diabolical lies told to you" before encouraging women to remain homemakers.

It's not a common phrase, so easy to see why people are connecting the two -- though whether there's any actual fire to this smoke is hard to say.

Of course, Travis Kelce called Harrison a great guy ... so hard to imagine Jason's stepping on Travis' toes here -- but, hey, brothers don't always see eye to eye.