Reference for Shevuot 6:2

לעולם ר' ישמעאל וכי לא מחייב רבי ישמעאל לשעבר קרבן אבל מלקות חיובי מחייב

[if he transgresses unwittingly], but not to free him from lashes [if he transgresses wilfully].<span class="x" onmousemove="('comment',' According to this, our Mishnah, in enumerating four kinds of oaths, is referring to wilful transgression.');">²</span>

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