תלמוד על במדבר 33:2

A sheet of a Torah scroll must contain not less than three columns and not more than eight. As regards the lines [in a scroll] a reason was given [for four different numbers]: corresponding to the journeys,²⁷The reading of H and GRA. V and M have ‘in the journeys’. forty-two; corresponding to the myriads of Israel, sixty; corresponding to the elders of Israel, seventy-two; and corresponding to the reproofs in Deuteronomy, [36a] ninety-eight; all depending on [the size of] the script.²⁸The larger the characters the fewer the number of lines in a column.
‘Corresponding to the journeys,’ as it is said, And Moses wrote their goings forth.²⁹Num. 33, 2. As the expression of writing (wrote) occurs in the same context as the journeys (goings forth), the number of lines in a written column may be the same as the number of the journeys. ‘Corresponding to the myriads of Israel,’ as it is said, Write thou these words … and with Israel;³⁰Ex. 34, 27. Write and Israel (numbering sixty myriads) occur in the same context. as Israel numbered sixty myriads so may the lines of the Torah be sixty [in a column]. ‘Corresponding to the elders, seventy-two,’ as it is said, Gather unto Me seventy men³¹Num. 11, 16. … there remained … in the camp … of them that were recorded.³²ibid. 26. The number of the elders is found in the same passage as the expression of writing (recorded, lit. ‘written’). ‘Corresponding to the reproofs, ninety-eight,’ as it is said, If thou wilt not observe to do all the words of this law that are written.³³Deut. 28, 58, the words of this law refers to the reproofs numbering 98 and occurs with written in the same passage.
In the case of ḳelaf parchments no limit was prescribed, and one may add [as many lines]³⁴N.Y. explains, ‘sheets’. as desired, provided only there are not less than three columns [to the sheet].³⁵i.e. the lines in a column, or according to N.Y. the sheets, should not be so many as to leave less than three columns for the last sheet of the scroll.