Baba Basra 162a - Last Line of Contract

R. Yochanan says that there is a requirement to repeat a phrase of the contract in the last line, rather than right a new clause that doesn't appear earlier in the contract. The reason that nothing new can be written in the last line is because chazal instituted that any clause written in the last line of the contract is ignored. The rationale is that sometimes witnesses will leave a line between the end of the contract and the start of their signatures. There is a concern that the holder of the document will insert a clause that benefits him in that last line, therefore we have a rule that nothing can be learned from the last line.

There seems to be a machlokes between tosafos and the rashbam whether this is an actual takana that the contract should be summed up in the last line, or whether it is just a halacha that anything new written in the last line is disregarded. Rashbam seems to understand that we don't require the a the contract to be summed up in the last line, just that we will ignore anything new that is introduced in the last line. However, Tosafos (161a d.h. v'neichush, and v'tzarich) implies that since we institute the the contract must be summed up in the last line, if that is not done we invalidate the entire contract since it is prone to lead to forgery.

Both the Rashbam and Tosafos point out that the custom of writing שריר וקיים was only done for a shtar mekushar, not for a standard contract because that would have indicated an end to the contract and chazal would not have to institute the rule of not learning anything new from the last line of the contract. However, nowadays when we right שריר וקיים, Tosafos quotes from Rabbeinu Tam that even vital and new information can be written in the last line of the contract.

Practically, when we write gittin, we write ודן די יהוי ליכי מינאי ספר תרוכין ואגרת שבוקין וגט פטורין in the second to last line, and write כדת משה וישראל in the very last line. However, Tosafos points out that since כדת משה וישראל in a gett is equivalent to שריר וקיים of other contracts, one can technically write the entire statment of ודן די יהוי ליכי....כדת משה וישראל in the last line. But, Tosafos writes that after Rabbeinu Tam died they found in his writings that we are careful not to write anything important in the last line, therefore the statement of ודן די יהוי ליכי מינאי ספר תרוכין which is integral to the gett (dependent on the sugya of yadayim mochichos), cannot be written in the last line (because that is all part of the to'ref of the gett), only the words ואגרת שבוקין וגט פטורין כדת משה וישראל, which are repetitive can be written in the last line.

Although Tosafos ultimately holds like the original version of Rabbeinu Tam that we can learn from the last line since we write כדת משה וישראל, the Shulchan Aruch (e.h. 126:18) writes that לכתחלה the last line shouldn't contain anything more than כדת משה וישראל, so if the last line contained any part of the statement ודן די יהוי ליכי מינאי ספר תרוכין it would invalidate the gett. The Beis Shmuel (27) points out that the shulchan aruch seems to be more machmir than Tosafos, that לכתחלה we don't even allow ואגרת שבוקין וגט פטורין to be written in the last line, but bidieved we can even allow ודן די יהוי..ספר תרוכין to be on the last line since we write כדת משה וישראל.