Reference for Bava Kamma 86:22
וכן בבן או בבת ת"ר (שמות כא, לא) או בן יגח או בת יגח לחייב על הקטנים כגדולים
[I understand], What is taught by [the expression] If a slave? [It implied] that a slave [killed] unintentionally is subject to the same law as a slave [killed] intentionally. Now as regards Resh Lakish [who was of a different view in this respect] shall we also assume that just as he drew no lesson from the distinction between <i>'a slave'</i> and <i>'if a slave'</i>, so he drew no lesson from the distinction between '<i>kofer</i>' and 'if <i>kofer</i>'? — I may say that this was not so. From the distinction between <i>'a slave'</i> and <i>'if a slave'</i> he did not draw a lesson, whereas from the distinction between '<i>kofer</i>' and 'if <i>kofer</i>' he did draw a lesson. Why this difference? The expressions <i>'a slave'</i> and '<i>if a slave'</i> do not occur in the context dealing with payment,<span class="x" onmousemove="('comment',' It could thus hardly have any bearing on the law of payment. ');"><sup>19</sup></span>