Reference for Bava Batra 255:11
זה הכלל כל שתחלתו או סופו בפסלות פסול תחלתו וסופו בכשרות כשר
R. Abba sent to R. Joseph b. Hama: If a person possessed evidence<span class="x" onmousemove="('comment',' Lit., 'he knew'. ');"><sup>19</sup></span> in one's favour [in the matter of a plot of] land, before he became blind, and [then] became blind, he is disqualified.<span class="x" onmousemove="('comment',' From acting as witness, A blind man cannot possibly indicate the exact position of the boundaries of a field, though he may have known them well before he lost his eyesight. ');"><sup>20</sup></span> Samuel, however, said: He is permitted [to give evidence], [since] it is possible for him to gauge [the extent of] its boundaries; but [in the case of] a cloak [he is] not [to be admitted as witness].<span class="x" onmousemove="('comment',' Because many cloaks are equal in size. ');"><sup>21</sup></span> R. Shesheth said: Even [in the case of] a cloak [his evidence is admissible, for] it is possible for him gauge the measurements of its length and of its breadth; but not [in the case of] a bar of metal. R. Papa said: Even [in the case of] a bar of metal, [for] it is possible for him to gauge its weight. An objection was raised: 'If a person possessed evidence<span class="x" onmousemove="('comment',' V. p. 533, n. 8. ');"><sup>22</sup></span> affecting another before he became his son-in-law, and, [subsequently,] he became his son-in-law, [or if that witness] had the faculty of hearing and became deaf, the faculty of seeing and became blind, sane and became insane, he is disqualified [from giving evidence]. If, however, he possessed evidence affecting him before he became his son-in-law, and when he became his son-in-law, his daughter died; [or if he] had the faculty of hearing, became deaf, and regained his hearing; [or if he] had the faculty of Seeing, became blind, and regained his eyesight; [or if] he was sane, became insane, and regained his sanity, [in all these cases] he is qualified [to act as witness]. This is the general rule: Whenever his beginning<span class="x" onmousemove="('comment',' The time of his observation. ');"><sup>23</sup></span> or his end<span class="x" onmousemove="('comment',' When he appears for the purpose of giving evidence. ');"><sup>24</sup></span> was under a disqualification, he is disqualified, [but whenever] his beginning and his end [find him] in a suitable condition, he is permitted [to give evidence].<span class="x" onmousemove="('comment',' 'Ar. 17b. ');"><sup>25</sup></span>