Verse 12 began with the statement that he who could overlook the faults of the record would receive “greater things.” Now the suggestion that there might be faults surfaces again, and Moroni now indicates that the source of those faults was the men who made them. The message of the text comes from God, in whom there is no error. Nevertheless, the word of God comes through men, and that conduit allows for the introduction of humanity into the message of God. This message is so important for the modern reader of the text that Moroni repeats it in the final line of the Title Page: “And now, if there are faults they are the mistakes of men.”
[But behold, we know no fault]: With this statement Moroni testifies that there are no intentional errors in the text. The humanity of Mormon and Moroni might allow for errors, but they do not know that they are there. The implication is that if they knew that there was a fault, they would have corrected it.
[he that condemneth]: Moroni has apparently seen Joseph’s day, and this verse is beginning a transition from speaking to Joseph to speak to those who are immediately around Joseph as the text comes forth. In verse 12 we have the positive statement for the one who would believe in spite of human errors. Such a one would receive greater things. In this statement, the one who condemns the text because of those errors, and therefore will not believe in it, will be “in danger of hell fire.”
The source of the phrase “in danger of hell fire” would be Matthew 5:22, which is repeated in 3 Nephi 12:22. The contexts are completely different, so the borrowing is purely lexical. This is a phrase with which Joseph is familiar, and so it is used here.