It is arguably an allusion to Mosiah 25:16 (!) in the Book Mosiah, a part of the Book of Mormon, which pretty much sums up Smith's situation:
And he did exhort the people of Limhi and his brethren, all those that had been delivered out of bondage, that they should remember that it was the Lord that did deliver them.The graffiti is a pictogram that encodes a simple program (rotate all point symmetric glyphs) which is used to encrypt and decrypt a hidden message:
The letters M, U and A show mirror symmetry. The numbers 2, 5 and 1 have no symmetry at all. Only Z and 9 are point symmetric. The peculiar "u-turn" swirl on Z implies a rotation of 180° around its center. The result is identical: Z. Do the same to 9 and you arrive at 6.