[The ruling on plucking white hair]

The answer – and Allah is the One who grants success and support – is that the scholars of the madhhab have mentioned, as in al-Bayān and its marginal notes, that it is forbidden to pluck the hair of the pubic region and other than it, and they did not except from that except plucking the hair of the nose and the armpit.
And that which can serve as an indication for this is what came in a ḥadīth from the Prophet (May Allah bless him and his family and grant them peace), that he cursed the woman who joins hair (to another’s hair)... and so on, and he mentioned in it al-nāmiṣah [the woman who plucks], and they explained al-namṣ, as in al-Bayān, that it is plucking the hair of the pubic region, and it was said: It is plucking the hair of the forehead and the face. (A marginal note from Sharḥ al-Azhār. Completed, and (taqrīr) (Í)).
Then he said in al-Bayān, in enumerating the disliked matters with respect to the beard: “It is disliked to lengthen the beard with the hair of the temples, and to arrange it, and to whiten it with sulphur in order to display advanced age, and to pluck the white hairs from it, and to tie it, and to split it into two halves, and to twist it, and to leave the hair dishevelled and dusty.” End.

Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2