Reference for Yoma 147:3

רב אחא בר יעקב אמר למעוטי משחק בקוביא והא משחק בקוביא מדאורייתא מיחזי חזי ורבנן הוא דפסלוהו ולא קא חיילא עליה שבועה

applies only to those qualified to bear witness;<span class="x" onmousemove="('comment',' V. Shebu. 30a.');">⁵</span> and we raised the point: what does that mean to exclude, whereupon R'Papa said: This excludes a king, and R'Aha B'Jacob said: This excludes a professional dice-gambler.<span class="x" onmousemove="('comment',' The king can neither testify, nor be testified against, because of his exalted position; the gambler cannot testify, because his profession renders him, hence his statements or pledges, untrustworthy.');">⁶</span>

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