Bava Batra — Daf 34a

היכי נידיינוה דייני להאי דינא לישלם ליכא תרי סהדי ליפטריה איכא חד סהדא לישתבע הא אמר מיחטף חטפה וכיון דאמר דחטפה הוה ליה כגזלן

אמר (להו) רבי אבא הוי מחויב שבועה שאינו יכול לישבע וכל המחויב שבועה שאינו יכול לישבע משלם

א"ל אביי מי דמי התם סהדא לאורועי קאתי כי אתי אחרינא בהדיה מפקינן לה מיניה הכא לסיועי קא אתי כי אתא אחרינא מוקמינן לה בידיה

אלא אי דמיא הא דרבי אבא לחד סהדא ולתרתי שני ולפירי:

How are the judges to decide this case? Shall we make him pay? — There are not two witnesses against him. Shall we let him off scot free? — There is one witness.  Shall we administer an oath to him? — But he admits that he snatched the article, and since he admits that, he is, as far as this case goes, a robber.  Said R. Abba to him: He is [in the position of a man who is] legally under obligation to take an oath and is yet unable to take it; and the rule is that whoever is under obligation to take an oath which he cannot take must pay.  Abaye, however, said to the Rabbis: Are the two cases on all fours? [There in the case of the bar of metal] the witness comes to oppose [the defendant], and if there were another witness with him we should make him give up the article. Here [in the case of the land] the witness comes to support [the defendant], and if there were another witness we should confirm his title to the land.  If you do wish to draw a parallel with the case of R. Abbah, it would be in the case of one witness [who testifies that the occupier has had the use of the land] two years, and [where the claim is for] the produce.