Reference for Bava Batra 325:7

אמר רב לא שנו אלא בין עדים לכתב אבל בין עדים לאשרתא אפילו טובא נמי כשר

R. Abbahu said: As [much] for instance [as is necessary for the writing of] Baruk b. Levi<span class="x" onmousemove="('comment',' [H] contains two letters which extend downwards and one which runs upwards. ');">¹⁸</span> in one line; [for] he holds the opinion [that the limit is] one [written] line and two [intervening] spaces. Rab said: What has been taught<span class="x" onmousemove="('comment',' Regarding the limit to two lines of the blank space allowed below the text of a deed. ');">¹⁹</span>

Jastrow