Yoreh Deah Siman 18 Seif 4

 

ד סַכִּין שֶׁתִּבָּדֵק בְּהוֹלָכָה וְלֹא הִרְגִּישׁ שֶׁיֵּשׁ בָּהּ פְּגָם, וּכְשֶׁהֶחֱזִיר אוֹתָהּ בַּהֲבָאָה הִרְגִּישׁ שֶׁיֵּשׁ בָּהּ פְּגָם, וְזוֹ הִיא הַנִּקְרָא מְסֻכְסֶכֶת, אִם שָׁחַט בָּהּ דֶּרֶךְ הוֹלָכָה וְלֹא הֵבִיא, שְׁחִיטָתוֹ כְּשֵׁרָה; וְאִם הֵבִיא, שְׁחִיטָתוֹ פְּסוּלָה. וְהָנֵי מִלֵּי כְּשֶׁהִרְגִּישׁ בָּהּ קֹדֶם שְׁחִיטָה, אֲבָל אִם מָצָא סַכִּינוֹ יָפָה קֹדֶם שְׁחִיטָה, וְאַחַר שְׁחִיטָה מָצָא בָּהּ פְּגִימָה מְסֻכְסֶכֶת, וְאָמַר: בָּרִי לִי שֶׁלֹּא עָשִׂיתִי אֶלָּא הוֹלָכָה לְבַד, שְׁחִיטָתוֹ פְּסוּלָה.

 

Seif 4

If one inspected a knife (in one direction) and didn’t feel a flaw, if he checks another time (in a different direction) and he feels a flaw, this checking is to be disputed, if you slaughter in the direction that the checking was conducted (without a flaw) and did not reverse the direction, the slaughter is acceptable. If perhaps he reversed the direction, the slaughter is unacceptable.

And one who cuts and doesn’t feel the flaw before the slaughter, only if we found his knife acceptable before the slaughter; however (now) after the slaughter we find a disputable flaw, as it is said: it is clear me that if he cut in only one direction, the direction without flaw alone, the slaughter is unacceptable.