Parashas Vayikra · Aliyah 7 · Passuk 4
Chabad.org — English translation + Rashi
Torah Temima points to Shevuot 18a–29a / Toras Kohanim on shevuat bitui.
E-Daf / Tsurras Hadaf
PDF of the daf / source
English: Or a person who swears, uttering with the lips to do harm or to do good… and it is hidden from him.
Shevuat bitui — an oath about a future or past act that is then violated or forgotten.
One who makes a verbal oath to do or not do something (for good or for harm) and later, through forgetfulness, violates it, is liable under this chapter’s framework.