Ali's full statement:
I am deeply saddened by the passing of Mr. Mandela. His was a life filled with purpose and hope; hope for himself, his country and the world. He inspired others to reach for what appeared to be impossible and moved them to break through the barriers that held them hostage mentally, physically, socially and economically. He made us realize, we are our brother’s keeper and that our brothers come in all colors.
What I will remember most about Mr. Mandela is that he was a man whose heart, soul and spirit could not be contained or restrained by racial and economic injustices, metal bars or the burden of hate and revenge. He taught us forgiveness on a grand scale. His was a spirit born free, destined to soar above the rainbows. Today his spirit is soaring through the heavens.
He is now forever free.
A boxer himself, Mandela was a huge fan of Ali.
"Ali's struggle made him an international hero," Mandela said following his release from prison in 1990. "His stand against racism and war could not be kept outside the prison walls."
Here's video of the two icons playfully sparring: