פירוש על בבא בתרא 56:5

There, "And Warning in his owner (he has already been warned with witnesses)" said the merciful-one (as written in the Torah)... - As if meaning to say: (they are) not similar (the case of the bull to that of property) even though we learned three years from three gorings, just as we remove these from (their) chazaka also these we take out from (their) chazaka. But (in regards to the subject of) claims (of property) from warning (of the bull) we don't have (a way to) learn it (no comparisson), that there, since from warning (with witnesses is what obligates him to pay) money over his gorings it is, she (the warning is what) comes and establishes his bull in the Chazaka of '(fore)warned'. We need (this warning to be) in front (of the) owners (so that they) will know (to have a chance) to argue and contradict the witnesses and (have a chance) to bring others (so as) to (testify against these initial witnesses so that they wil become) false (witnesses). But (the) reason for the claim (over the property is so that) he be cautioned to be careful with (proving) his merit (to be there) is (the reason) that she (the warning) comes, that this (warning) claims that through stealing, she (the property) is in his hands (so he should be careful), (therefore) here (in our case) even though that (the claim was) not infront of him it also is (a valid claim, since he is already in an instant possition to lose his property).

Of your friend a friend he has... - And was said this (one) to this (one), and the matter comes to his ear and (it is) not possible (for him to defend himself) to say "had I heard I would have been careful in proving (with a document) my merit (to possess the land)" (since we assume he heard the complaint of the previous owner)