"I assume you know the difference".
The panel voted along party lines to authorize a subpoena in case Whitaker fails to show up or declines to answer certain questions.
The stalemate ended Thursday evening after the committee chairman, Nadler of NY, said the committee would not issue a subpoena if Whitaker appeared voluntarily.
"We have followed the special counsel's regulations to a T", Whitaker said.
Mr Whitaker - who leads the US Department of Justice - has refused to offer any details regarding the investigation or his opinions of it, and only stated he has been briefed on the special counsel's inquiry.
Asked about Whitaker's congressional appearance, Trump called Whitaker an "outstanding person" and said he would do very well should he testify. William Barr, who is likely to be confirmed as attorney general next week, also testified last month that he believed Mueller was not on a witch hunt.
"I'm thinking maybe we just set up a popcorn machine in the back, " said Rep. Doug Collins, the committee's top Republican.
Whitaker had threatened not to show up to the hearing after Democrats approved a subpoena if he didn't answer all their questions, but the committee chairman dropped the threat Thursday night.
The remark drew gasps in the hearing room, where committee chairmen hold vast power, including over who asks the questions and for how long.
Instead, Whitaker said he has not interfered with Mueller's investigation into Russian meddling in the 2016 election, including the possibility that Trump's campaign colluded in that effort.
Many of the Democrats have reservations about Barr that hinge on how he will treat Mueller's investigation.
"Mr. Attorney General, we're not joking here, and your humor is not acceptable", the congresswoman responded.
After Whitaker objects, Raskin admonishes him that "this is my time". He said Mueller would finish on his own schedule.
Hours before the hearing on Friday, Nadler and Democratic heads of several other House panels renewed a call for Whitaker to produce documents regarding his prior work with the company World Patent Marketing. The president himself kept an eye on the proceedings before leaving the White House for his annual physical.
(Nota bene: Whitaker was under oath.) My observations are in the chronological order that Whitaker said them.
Whitaker stunned onlookers when he told House Judiciary Committee Chairman Jerrold Nadler, D-N.Y., that his time slot had expired as Nadler asked Whitaker if he'd been "asked to approve any requests or action" for the special counsel. Whitaker has come under scrutiny for his involvement with the invention promotion company, which was accused of misleading consumers.
The Russia investigation into Trump campaign ties and possible obstruction of justice has been highly politicised since Mr Trump's firing of FBI Director James Comey in May 2017.