The Talmud on Spelling in a Torah Scroll

[Similarly, one should not write] bent [letters like kaf and nun found in the middle of a word as] straight [letters like kaf and nun found at the end of a word, nor should one write] straight [letters as] bent [letters. A final] mem [should not be written like a] samekh, [and a] samekh [should not be written like a] mem. [A]‌ closed [mem should not be written] open, [and an] open [one should not be written] closed. [Similarly, if there is] an open paragraph [in the Torah] one may not render it closed, [and] one may not render a closed [paragraph] open. [If] one wrote [a mezuzah or a Torah scroll] following the [Torah’s format] for poetry or if one wrote poetry like [regular text, as a mezuzah is typically written,] or if one wrote without ink [but with another material,] or if one wrote the mentions [of God’s names] in gold, [all of] these must be suppressed.