Mishnah Berurah — משנה ברורה

From the hole - This is referring to when it was not sewed up [after it tore], and it is coming to inform us that [this applies] even though there did not remain the full [measurement of the length of the thumb from the] knuckle [to the end of the nail from the place of the tear to the edge of the garment]; and it is similar to what was written above in siman 11, se'if 10, that it is only required to have that measurement at the time of making/affixing [the ציצית onto the garment]. And if one wants to sew up the tear - then, if the garment is of wool, he may sew it up with threads of any other material, and he does not need to untie to the ציצית from the corner and then re-tie them a second time after he sewed it since the corner was not invalid; and if the garment is of other materials, it is forbidden to sew it with threads of the same material according to Rashi, for perhaps he will leave over some of those threads to be used as ציצית strings. And even if there are already ציצית there, it makes no difference. Rather, he should use threads of another material. And it is better to not sew with white threads, rather to only use colored threads, for nowadays we only make our ציצית white and therefore we would not be concerned that he might leave over from the sewing threads to be used as ציצית strings.