I noticed the expression, "the fountain of all righteousness" as I read Ether 8:26 the other day, and found it to be a unique Book of Mormon expression. It probably originates from Lehi when he in 1 Nephi 2:9 speaks to Laman and says
O that thou mightest be like unto this river, continually running into the fountain of all righteousness!
Although one could always speculate that Lehi got this expression from the brass plates. In any case, this expression from the small plates of Nephi is probably what Moroni has in mind when he says in Ether 8:26
Wherefore, I, Moroni, am commanded to write these things that evil may be done away, and that the time may come that Satan may have no power upon the hearts of the children of men, but that they may be persuaded to do good continually, that they may come unto the fountain of all righteousness and be saved.
If Lehi didn't make it clear that he was referring to Christ, Moroni does. The third and last time this expression is used is in Ether 12:28, where Christ himself verifies it is him
Behold, I will show unto the Gentiles their weakness, and I will show unto them that faith, hope and charity bringeth unto me—the fountain of all righteousness.
In the Webster 1828 dictionary, the first meaning listed for the word, fountain, is "spring or source of water". Christ told the woman at the well in John 4:14
But whosoever drinketh of the water that I shall give him shall never thirst; but the water that I shall give him shall be in him a well of water springing up into everlasting life.
There are also several Book of Mormon passages that describe Satan as the "enemy of all righteousness". See e.g. Alma 34:23 and Mosiah 4:14
