LATEST REPORT: Rep. John Lewis released from hospital

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1. Lewis was physically attacked and injured several times marching for civil rights in the '60s. 2. He was the youngest speaker in 1963's March on Washington. 3. President Obama awarded Lewis the Medal of Freedom, the highest honor a civilian can receive. 4. Lewis has spent decades protesting injustice. He has been arrested 45 times, including 5 times as a congressman. 5. He has also written several acclaimed books, including a graphic novel about Selma.

UPDATE 7:15 P.M.: U.S. Rep. John Lewis was released from the hospital Sunday evening, according to a spokeswoman for the congressman. 
"Rep. John Lewis has been released from the hospital this evening. All tests have been completed, and doctors have given him a 'clean bill of health.' He thanks everyone who shared their thoughts, prayers and concerns during his stay," according to Brenda Jones.

ORIGINAL STORY: U.S. Rep. John Lewis remained hospitalized Sunday afternoon for what was described as "routine observation" after he fell ill Saturday on a flight to Atlanta.

The 78-year-old civil rights icon was on a flight from Detroit when he started feeling dizzy and sweaty, an aide said Saturday night.

After being hospitalized in Atlanta, the Democrat’s office said in a statement Saturday evening that he was expected to be released Sunday.

On Sunday afternoon, an update from the congressman's spokeswoman Brenda Jones said that he was "resting very comfortably and fully expects to be released very soon."

The statement continued, "He is grateful for the concerns and well wishes of Georgians, colleagues, family and friends."

In addition to noting that Lewis remained in the hospital until the doctor's observations are completed, the statement said, "Please stand by for official news regarding his condition."

No other details were provided about his condition.

Lewis has represented Georgia’s 5th Congressional District since 1987.

RELATED: Five things to know about John Lewis

He was among key activists in the civil rights movement, taking part in the Nashville lunch counter sit-ins, the 1961 Freedom Rides, the 1963 March on Washington and the Bloody Sunday march in 1965, where he was beaten in the skull by a state trooper in Selma, Alabama.

The septuagenarian hasn't been slowing down lately. Just last month he joined thousands of people marching in Atlanta as part of the nationwide March For Our Lives against gun violence.