Mishnah for Kilayim 9:10
אוֹתוֹת הַגַּרְדִּין וְאוֹתוֹת הַכּוֹבְסִים, אֲסוּרוֹת מִשּׁוּם כִּלְאָיִם. הַתּוֹכֵף תְּכִיפָה אַחַת, אֵינָהּ חִבּוּר, וְאֵין בָּהּ מִשּׁוּם כִּלְאַיִם, וְהַשּׁוֹמְטָהּ בְּשַׁבָּת, פָּטוּר. עָשָׂה שְׁנֵי רָאשֶׁיהָ לְצַד אֶחָד, חִבּוּר, וְיֶשׁ בָּהּ מִשּׁוּם כִּלְאַיִם, וְהַשּׁוֹמְטָהּ בְּשַׁבָּת, חַיָּב. רַבִּי יְהוּדָה אוֹמֵר, עַד שֶׁיְּשַׁלֵּשׁ. הַשַּׂק וְהַקֻּפָּה מִצְטָרְפִין לְכִלְאָיִם:
The marks of weavers [e.g. initials stitched on] and the marks of launderers are not subject to the laws of <i>kilayim</i> [if the thread used is wool and the garment is linen]. If one makes a single stitch [through two materials] it is not [considered] a connection [for the laws of impurity] and are not subject to the laws of <i>kilayim</i>. If one pulled out [the single stitch] on the Shabbat, he is exempt [from punishment]. If one brings both ends [of the single stitch] to the same side [he made two stitches], it is [considered] a connection, and are not subject to the laws of <i>kilayim</i> and the one who pulls it out on Shabbat is liable. Rabbi Yehudah says, [it is not a connection] unless one made three stitches. A sack and a basket, combine for <i>kilayim</i> [if one has a strip of wool and the other a strip of linen that are fastened together].