Reference for Bava Kamma 130:5

אמר רבא לעולם דמעיקרא שויא ארבעה והשתא נמי שויא ארבעה ודקא קשיא כפילא ד' וחומשיה זוזא הב"ע כגון שנשבע וחזר ונשבע ארבע פעמים והודה והתורה אמרה וחמישיתיו

it might be said that [we are dealing here with a case] where e.g., he took an oath and repeated it four times, after which he confessed, and as the Torah says 'and its fifths',<span class="x" onmousemove="('comment',' E.V.: 'and the fifth part thereof'. ');">⁷</span> the Torah has thus assigned many fifths to one principal.<span class="x" onmousemove="('comment',' I.e., a fifth will be paid for each false swearing. ');">⁸</span>

Jastrow