Muhammad said. That is authority. That we accept. We accept Muhammad as the representative of God. Whatever he says, we accept, that's all. What he meant, that is his business. But he is authority. He said that "This is the name of God. You chant, you pray, Allah-u akbar." That's all. That is authority.

…Here is the perfect holy man. He never says that "You chant my name." He said, "Chant Allah's name." That is holy man. That is test of holy man. He does not become God; he serves God. That is holy man.

…We accept Muhammad's authority. That's a fact. He's authority.

(Srila Prabhupada, Conversation — March 14, 1975, Tehran)