(CNN) The music of Aretha Franklin "strengthened," "revived" and encouraged civil rights activists to "keep the faith" in their cause during the '60s, civil rights icon John Lewis said of the legendary singer who died Thursday.

While many of Franklin's mourners paid tribute to her voice and her songs, Lewis praised Franklin's involvement and contributions to the civil rights movement.

"We have lost one of the great spirits of our time," the Georgia congressman told CNN's John King on "Inside Politics" Thursday. "Aretha inspired all of us with her unbelievable capacity and ability to make us smile, to dance, to be happy. She was just a wonderful, beautiful soul."

The civil rights leader said he'll "never forget" Franklin's performance at the 1967 Southern Christian Leadership Conference in Atlanta, the group led by Martin Luther King, Jr.

"She was singing and she got happy and kept singing. And Dr. King asked someone to go over and tell Aretha, 'We got to close it out, it's getting late.' But she was feeling so good about being there to perform for Dr. King and the movement. That was the last performance that Dr. King witnessed of hers," Lewis recalled.

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