Reference for Sanhedrin 124:6
לא מיתוקמא ליה בעבודת כוכבים דקתני סיפא חומר בשאר מצות שבשאר מצות שגג בלא מתכוין חייב
But this cannot be so, for when Raba propounded to R. Nahman, 'What if one is unaware of both [i.e. that it is the Sabbath, and that labour on the Sabbath is forbidden],' his problem was whether one sacrifice is incurred or two [one for each act of work]; but none maintain that he is entirely exempt? What difficulty is this! Perhaps after all, it ought be said, the first clause [dealing with the greater severity of the Sabbath] refers to idolatry, whilst the second treats of other precepts; the unwitting and unintentional transgression of which consisted of thinking that [melted forbidden fat] was spittle, which he swallowed. [For this, liability is incurred,] which is not so with regard to the Sabbath, there being no liability [in an analogous case, e.g.,] if one intended lifting something detached from the soil, but accidently tore out a plant from the earth, he is exempt from a penalty.<span class="x" onmousemove="('comment',' Cutting or tearing out anything growing in the earth is a forbidden labour on the Sabbath. His offence was both unwitting and unintentional for (i) he had no intention of tearing out anything and (ii) he did not know that this was growing in the soil, Now, had he known that it was growing in the soil and deliberately uprooted it in ignorance of the forbidden nature of that action, his offence would have been unwitting but intentional. By analogy, had be intended to eat the melted fat, thinking that it was permitted, his offence would be regarded as unwitting but intentional. Since, however, he did not intend eating it at all, but accidentally swallowed it, thinking at the same time that it was spittle, his offence was both unwitting and unintentional. ');"><sup>5</sup></span>