Here the original manuscript reads “towards the heavens”, which Oliver Cowdery accidentally miscopied as “towards heaven” in the printer’s manuscript. In other words, he omitted the definite article the and reduced the plural heavens to the singular heaven. The printed editions have continued with the reading in 𝓟, but the critical text will restore the original the heavens in Alma 31:14 since there is nothing inappropriate about it.
Elsewhere in the Book of Mormon text, there are 38 occurrences of the heavens. When the preposition is toward(s), we have three examples of “toward(s) heaven” (in 3 Nephi 11:5, 3 Nephi 11:8, and 3 Nephi 17:24), but none of “toward(s) the heavens”. Yet we do get instances of the heavens with other prepositions besides toward(s), such as these examples, with the second one being a quote from the King James Bible (Isaiah 51:6):
Summary: Restore in Alma 31:14 the plural the heavens, the reading of the original manuscript; this phraseology is indirectly supported by usage elsewhere in the text.