President Trump on Thursday mourned the death of Rep. Elijah Cummings, tweeting that the late congressman and fierce critic of the administration would be “hard, if not impossible, to replace.”

“My warmest condolences to the family and many friends of Congressman Elijah Cummings. I got to see first hand the strength, passion and wisdom of this highly respected political leader,” Trump tweeted. “His work and voice on so many fronts will be very hard, if not impossible, to replace!”

Cummings died early Thursday morning “due to complications concerning longstanding health challenges,” his office said. He was 68.

Read more at The Hill.