Reference for Bava Batra 325:4

וכמה אמר רב יצחק בן אלעזר כגון לך לך זה על גבי זה אלמא קסבר שני שיטין וארבעה אוירין

And how much [space]?<span class="x" onmousemove="('comment',' Is implied by the limit of 'two lines'. ');">⁹</span> — R. Isaac b. Eleazar said: As [much] for instance [as is required for the writing of] Lak Lak<span class="x" onmousemove="('comment',' [H] to thee, to thee, (or perhaps [H] get thee out, a clause from Gen. XII, 1). There must be sufficient space for allowing of the writing, in each of the two lines, of letters which extend upwards ([H]) and downwards ([H]) without their touching each other. These letters, furthermore, are to be in the larger kind of character as reported above in the name of Hezekiah. Cf. supra note 6. ');">¹⁰</span> above one another. This shows that he is of the opinion [that the limit is] two [written] lines and four [intervening] spaces.<span class="x" onmousemove="('comment',' Two between the lines (for the [H] of the upper, and the [H] of the lower line), one above the upper line for the [H], and one space below the lower line for the [H]. Thus: [H] ');">¹¹</span>

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