Reference for Bava Batra 307:1
ראיה במאי רב הונא אמר ראיה בעדים רב חסדא ורבה בר רב הונא אמרי ראיה בקיום השטר
In what [manner is] proof [produced]?<span class="x" onmousemove="('comment',' This question may apply to the statements of both R. Meir and the Sages. ');"><sup>1</sup></span> — R, Huna said: Proof [is produced] by witnesses.<span class="x" onmousemove="('comment',' Who testify as to the state of the health of the donor at the time the gift was made. ');"><sup>2</sup></span> R. Hisda and Rabbah, son of R. Huna, said: Proof<span class="x" onmousemove="('comment',' Required by the Sages. (For the proof required by R. Meir, v, infra.) ');"><sup>3</sup></span> [is produced] by the attestation of the deed.<span class="x" onmousemove="('comment',' The signatures of the witnesses on the deed must be verified before a court, and only when the validity of the deed had been established, independently of the donor's admission, have the donees established their right to the ownership of the gift. ');"><sup>4</sup></span>