Mishnah Berurah — משנה ברורה

On the Rambam who deems it as fit - Even if he did the inserting [of the strings into the hole] and also the knots and winded sections without intent. For he holds that even though it's required that the strings be spun for the sake of the mitzvah, nevertheless, the inserting does not have to be [done] for the sake of the mitzvah. And he derives it from [the fact that] the verse says "...[speak to] the Children of Israel..." (Numbers 15:38), which excludes non-Jews; we conclude from it that [if it was made by] a Jew without intent, it is valid. And don't ask: [Why not] remove [the strings] from the garment and then go back and put them on with intent, for the sake of the mitzvah? We can answer that we are referring to when it is close to Shabbos and there is no time to remove and re-tie them. Or [we can answer that we're talking about a case] where one of the ends [of one of the strings] became severed, and if he would remove it, it would be forbidden to go back and put in on the garment, as we mentioned above in Siman 12.