Bava Batra 323:1
אמר רב עמרם לפי שאין למדין משיטה אחרונה
— R. Amram said: Because the last line cannot be taken as a determining factor.<span class="x" onmousemove="('comment',' Lit., '(people) do not learn from the last line'. Witnesses do not as a rule take care to write their signatures immediately below the text of the deed, and usually leave some space between their signatures and the text. As this space might be used by the unscrupulous for the insertion, in his own interests, of an unauthorised line, it has been provided that nothing essential that has not already appeared in the text of the deed may appear in its last line. Consequently, should this line ever contain a vital point not recorded in the text, it would immediately be detected as spurious. ');"><sup>1</sup></span>
מאי שנא שני שיטין דלמא מזייף וכתב שיטה אחת נמי מזייף וכתב אלא לאו שמע מינה אין למדין משיטה אחרונה שמע מינה
you [derive] this? [The other] replied to him: Because it was taught, If the [signatures of the] witnesses were removed two lines from the text, [the deed] is invalid; [if only] one line, [it is] valid. Why are two lines different [from one line]? Because one might commit forgery and add<span class="x" onmousemove="('comment',' Lit., 'write'. ');"><sup>3</sup></span> [some unauthorised matter]! [In the case of] one line also [might not one] commit forgery and add<span class="x" onmousemove="('comment',' Lit., 'write'. ');"><sup>3</sup></span> [some spurious matter]? Must we not then conclude [that] the last line cannot be taken as a determining factor'? This proves it.