Rif Pesachim 8a {Pesachim 30a continues ... 30b}

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8a

{Pesachim 30a continues}
and Shmuel said: they need not be broken, but rather they should be kept until after their time {of prohibition=after Pesach} and utilized, whether with its kind or not its kind.
And the halacha is like Shmuel, for he holds like Rabbi Shimon.

They learnt {in a brayta}: One should not knead dough with milk, and if he kneaded, all the bread is forbidden, because of hergel aveira {=it leads one to sin}.
{Pesachim 30b}
Similarly, one should not grease an oven with fat {which is fleishig}, and if he greased it, all the bread is forbidden, until the oven is refired. And if he made it {the loaf} different like the eye of an ox it is permitted, for since he made it different, it is known that he did this to make it recognisable such that he does not come to have a problem, and thus it is permitted.

And a tiled pan which is generally used to bake chametz, one is forbidden to use it to bake matzah on Pesach, because it is fired from the outside. But if he filled it with coals {the coals being under it and the bread on top} and fired it from the inside, it is fine.

And these knives, on Pesach, one boils them and their handles in boiling water