The quote is often attributed to Emanuel Lasker, though finding the exact original source can be a challenge.
You can find a notable reference to this quote in the book "Capablanca's Hundred Best Games of Chess" by Harry Golombek. In this book, Golombek discusses the contrasting styles of Capablanca and Alekhine. He highlights how Capablanca's clear and methodical play made his moves seem inevitable and unstoppable, while Alekhine's unpredictable and imaginative style posed a different kind of challenge to his opponents.
Golombek attributes the quote to Emanuel Lasker, who was known for his keen commentary on the games of his contemporaries.