Senate Finance Committee Chairman Chuck Grassley issued a statement defending the whistleblower who filed a complaint about President Trump’s phone call with Ukrainian President Volodymyr Zelensky in July.

The conversation garnered national interest after it was revealed that Trump urged Zelensky to investigate former Vice President Joe Biden and his son, Hunter Biden, over the younger Biden’s work in Ukraine. Following the release of the transcript, the president has maintained that nothing in the call is worthy of impeachment, which is now under consideration, and he has publicly attacked the whistleblower.