Sen. Josh Hawley, R-Mo., a former clerk for Chief Justice John Roberts, called the justice's admonishment of both President Trump's legal team and the House Democratic impeachment managers' language late Tuesday night "extraordinary."

Hawley, who clerked for Roberts during the 2007-2008 term, said Wednesday afternoon he had "never heard him deliver an admonishment like that from the bench ever."

"He chooses his words very very carefully," Hawley said. "He cited a 1905 case impeachment case in which ... one of the sides was ... using language that was thought to be inappropriate. And so while he was careful to ... I think ... to be even-handed about it as is appropriate judicially, it's very clear what the impetus for that was ... [Rep. Jerry] Nadler getting up and calling the president's counsel a bunch of liars."

Nadler began the historic spat by speaking in support of the day's eighth amendment, which was proposed by Senate Minority Leader Chuck Schumer, D-N.Y., just as the clock struck midnight. The proposal would have amended the trial rules offered by Senate Majority Leader Mitch McConnell, R-Ky., to immediately subpoena former National Security Advisor John Bolton. Nadler said GOP senators would, "betray [their] pledge to be an impartial juror," and "be complicit in the president's coverup," if they did not vote for the Schumer amendment.

Then, Trump attorney Jay Sekulow hammed Nadler for suggesting that executive privilege, a longstanding constitutional principle protecting executive branch deliberations from disclosure, wasn't legitimate. Additionally, he accused Democrats of hypocrisy given that Attorney General Eric Holder had similarly cited executive privilege to avoid providing documents as part of House Republicans' "Fast and Furious" gunrunning probe.

The outbursts prompted Roberts, who as chief justice of the United States is constitutionally required to serve as the presiding judge in the impeachment trial, to issue his rebuke.

"It is appropriate at this point for me to admonish both the House managers and the president's counsel in equal terms to remember that they are addressing the world's greatest deliberative body," Roberts said. "One reason it has earned that title is because its members avoid speaking in a manner, and using language, that is not conducive to civil discourse."

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Roberts continued: "I do think those addressing the Senate should remember where they are."

Hawley, reflecting on Roberts' comments, said members of the Senate were aghast as the invective-laden spat occurred in the middle of impeachment proceedings Democrats have called "solemn."

"I mean, that's an extraordinary thing to say on the floor the United States Senate the middle of the trial and that's what drew the rebuke and rightly so," he said. "I can tell you, there was an open, open gasping on the Senate floor when Nadler was saying these things."

Fox News' Gregg Re and Jason Donner contributed to this report.