Donald Trump told his supporters not to believe any story citing anonymous "sources." Hmm.

Like a discounted hot dog or a call to your ex after a long night of drinking, anything that Republican candidate for president of the United States Donald Trump decides to tweet after midnight is probably ill-advised.

And the quick message he fired off in the early hours of Friday was no exception: "Anytime you see a story about me or my campaign saying 'sources said,' DO NOT believe it," he wrote. "There are no sources, they are just made up lies!"

Setting aside the widely-understood tenet of responsible journalism that gives a reporter the opportunity to protect the identities of one's sources when necessary, Trump's edict conflicts with another, more obvious set of rules: his own.

A cursory glance at the real estate mogul's own Twitter account proves, time and again, that Trump has presented his followers and supporters with dubious claims backed only by the word of unnamed "sources."

Because the tweets are all easily accessible on Twitter, a public space, the surely weary volunteer corps of Trump fact-checkers immediately emerged to present us with the candidate's own unsubstantiated claims from the past.

As Twitter user @MaxTemkin noted, Trump had no problem launching an entire movement targeting the birth certificate of President Barack Obama based solely on the word of an anonymous source.

In fact, Obama has apparently been the subject of many of the reports from unnamed "sources" — among them a "confidential source," and a couple of "extremely credible sources" — who have reached Trump's ears.

Of course, sometimes the "anonymous sources" that appear in news reports are actually Trump himself, as the New York Times' Maggie Haberman noted, tweeting that the billionaire had a penchant in the past for himself calling New York City papers as a "source close to Trump" to tip them off.

In fact, sometimes even when the sources dishing about Trump's personal life to the press aren't anonymous, they were oftentimes still him. Such was the case in the 1970s, 80s and 90s, when Trump, posing as his own public relations manager under the pseudonyms "John Miller" or "John Barron," would call reporters with details about his own life, according to the Washington Post.

At the end of the day, when it comes to media credibility in 2016, everything you read is best taken with a grain of salt and an air of skepticism. When it comes to the credibility of Donald Trump's Twitter feed in 2016, however, it's best taken with a mountain of the heavy-duty road salt that they use to clear highways in the winter.