The Bible says no man can see God. How can we believe that Joseph Smith did?
There is a good basis for your question. Exodus 33:20 quotes the Lord saying that “no man shall see me, and live.” John 1:18 states, “No man hath seen God at any time; the only begotten Son, which is in the bosom of the Father, he hath declared him.” John 6:46 is similar: “Not that any man hath seen the Father, save he which is of God, he hath seen the Father.” But do these verses really mean that man cannot see God under any circumstances? It seems to suggest that those who are “of God” can see Him, and there are many cases in the Bible that support this concept. For example, in Old Testament times, Moses and others saw God. Consider Exodus 24:9-11: 9 Then went up Moses, and Aaron, Nadab, and Abihu, and seventy of the elders of Israel: 10 And they saw the God of Israel: and there was under his feet as it were a paved work of a sapphire stone, and as it were the body of heaven in his clearness. 11 And upon the nobles of the children of Israel he laid not his hand: also they saw God, an