Bismillahi Al-Rahmani Al-Rahim

Tahara: Sunnas of the Body

Q 1
Would a regular toothbrush suffice as miswak? Also, lets say you are
fasting, and its makruh to use a miswak after dhuhr for someone who is
fasting, but its also good to use the miswak before 'Asr prayer, what is the
best one can do here? Is abandoning the act superior, or no?

Al-Raud Al-Murbi` indicates that using the finger, a rag, or the like do not fulfill the sunnah since they have not been mentioned in textual evidence. Based on this it seems that using a toothbrush would probably not fulfill the sunnah. This is according to Al-Raud Al-Murbi` and Nail Al-Ma'arib. But in Manar Al-Sabil it indicates that fulfilling the sunnah is based on cleaning the affected area.

As for someone fasting: after Zuhr it superior not to use miswak. While it is desirable for someone who is not fasting to use miswak before the `Asr prayer, it is makruh for someone who is fasting. So in this case it is more meritorious to not use miswak.

And Allah knows best.

 I currently am unable to grow a beard, except some hairs that I can grow
on the chin and under the neck and the like. Can I shave what is under the
neck (and whatever there is on the sideburns) and leave what is on the chin
until I am able to grow a beard?

Yes, it is permissible to shave what is under the neck. As for the sideburns, I have read that Imam Ahmad (Allah be pleased with him) did trim. I have not seen anything specifically mentioning shaving them, but doing so should not be unlawful since the sideburns (al-`aridan) are not part of the beard (al-lahya).

And Allah knows best.

What do you mean by 'closely cut[ting]' the mustache, and why is it
better than trimming?

What is meant by "closely cutting" is to trim it down to stubble. It is considered superior to shaving it or slightly trimming it based on understanding of the textual evidence and the practice of early Muslims--but all three do have their basis.

And Allah knows best.

What is the hukm in the Hanbali madhhab on dyeing one's hair black? What
about removing gray hair? What about the use of henna? What is the sunnah
for dyeing?

Plucking out grey or white hairs is offensive. So is dying the hair black, unless done for the sake of jihad. But it is a sunna to dye with henna.

And Allah knows best.

Please see the message from 9/28/2002 "Re: Questions for Lesson 01 and 02" for more details on these questions.

wa al-salamu `alaykum