Genesis 2:2 - Clarke's commentary and critical notes on the Bible

And on the seventh day God ended his work which he had made; and he rested on the seventh day from all his work which he had made. On the Seventh day God ended, etc. - It is the general voice of Scripture that God finished the whole of the creation in six days, and rested the seventh! giving us an example that we might labor six days, and rest the seventh from all manual exercises. It is worthy of notice that the Septuagint, the Syriac, and the Samaritan, read the sixth day instead of the seventh; and this should be considered the genuine reading, which appears from these versions to have been originally that of the Hebrew text. How the word sixth became changed into seventh may be easily conceived from this circumstance. It is very likely that in ancient times all the numerals were signified by letters, and not by words at full length. This is the case in the most ancient Greek and Latin MSS., and in almost all the rabbinical writings. When these numeral letters became changed for words at full length, two letters nearly similar might be mistaken for each other; ו vau stands for six, ז zain for seven; how easy to mistake these letters for each other when writing the words at full length, and so give birth to the reading in question.