He autographed one of his Islam pamphlets
I am the only owner, I Met Ali in an airport and asked for his autograph.
Thank you for contacting Mearto with your appraisal inquiry. Based on the photographs and description provided, the subject of this appraisal is a non-authenticated "Concept of Worship in Islam" pamphlet bearing a signature in blue ballpoint pen of boxing legend Muhammad Ali, with an inscription of "To Jackie from Muhammad Ali 1-26-89". According to the current owner, the piece was acquired from Ali first-hand in an airport.
The market for genuine Ali autographs is high, but any unauthenticated Ali autograph should carry a conditional classification due to the amount of forgeries that are available, even when the autograph does appear quite legitimate as this one does. A reputable third-party authentication service such as PSA could verify the signature if submitted to them for examination.
As for comparable sales, a similar pamphlet sold by Heritage Auctions in 2016 for $191.20, and a pair in 2019 sold for $312.00.
In consideration of the factors noted, a Fair Market Value (pre-auction estimate) of this piece conditional upon autograph authentication by a reputable third-party authenticator would be estimated at $150 to $200.