Imam Muhammad al-Taqi al-Jawad
Muhammad ibn ‘Alī ibn Mūsā (Arabic: محمد ابن علی ابن موسی ) (circa 12 April 811 - c. 29 November 835) was the ninth of the Twelve Imams and a descendant of the Prophet Muhammad. He was also called Abu Ja'far, Ibn al-Ridha ("the son of al-Riha); al-Jawād ("the generous") and al-Taqī ("the pious").
No, it is not obligatory to perform Salat before wearing Hirz of Imam Al-Jawad (AS).
It is not obligatory to take it off to go to shower.
Yes Imam Sadiq and the imams after him (peace be upon them) would of been from dark complexion as indicated by narrations.
We even have authentic ahadith which point towards the 12th imam’s mother being dark
أخبرنا أحمد بن محمد بن سعيد ابن عقدة قال حدثنا محمد بن المفضل بن قيس بن رمانة الأشعري و سعدان بن إسحاق بن سعيد و أحمد بن الحسين بن عبد الملك و محمد بن الحسن القطواني قالوا جميعا حدثنا الحسن بن محبوب الزراد عن هشام بن سالم عن يزيد الكناسي قال سمعت أبا جعفر محمد بن علي الباقر ع يقول إن صاحب هذا الأمر فيه شبه من يوسف ابن أمة سوداء يصلح الله عز و جل له أمره في ليلة واحدة
From Yazeed al-Kunaasee said, I heard Abaa Ja`far Muhammad bin `Alee al-Baaqir (عليهالسلام), he said: “Verily, the master of this affair (i.e. al-Qaa’im) in him is resemblance of Yoosuf (عليهالسلام), he is the son of a black bondswoman (female slave), and Allaah (عَزَّوَجَلَّ) will reform his affair in one night”
1. Al-Nu`maani, Kitaab al-Ghaybah, ch. 13, pg. 228, hadeeth # 8
2. Al-Nu`maani, Kitaab al-Ghaybah, pg. 163, hadeeth # 3
Imam Jawad (as) according to narrations would also be insulted for his darkness and given racist abuse. These realities found in our narrations are very different to what people try to depict the imams as in drawings.
Also Sister Amina Inloes has an interesting article about this topic which may benefit you; google and download the following article entitled:
'Racial ‘Othering’ in Shi‘i Sacred History: Jawn ibn Huwayy ‘the African Slave’, and the Ethnicities of the Twelve Imams'
May Allah grant you success
There are many narrations that Imam Musa Al-Kadhim (AS) and Imam Ali Al-Redha (AS) were of darker complexion. (Mawsoo'at Al-Mustafa Wal Etrah by Husain Al-Shaakiri, V. 13, P.13)
Imam Al-Jawad (AS)'s mother was from Africa, from the family of Lady Maria, the mother of Ebrahim, son of the Prophet Muhammad (SAWA).
We have many narration that some of his enemies used to call him Al-Aswad (The person with darker complexion).(Tafseer Al-Ayyashi 1: 314.).
We also have narrations that Imam Ali Al-Hadi Al-Naqi (AS) was of darker complexion. (Madeenatul Ma'aajiz by Sayyed Hashim al-Bahrani, V.3, P.504.)
Sheikh Mufid (r.a) and Ibn Shahr Ashoub (r.a) have only recorded one son for Imam Reza(a.s) and he is Imam Muhammad al-Taqi al-Jawad (a.s) but some other historians have recorded five sons and a daughter for him.
As for Imam Jawad (a.s) the sons are Imam Ali al-Naqi al-Hadi(a.s) and Musa al-mubarqa' who is buried in Qom( Chehel Akhtaran) and he also had a daughter named Hakimah Khatoon who is buried in Samerra,Iraq.
Sabeeka سبيكة النوبية was a great pious lady married to Imam Al-Ridha (AS) and mother of Imam Muhammad Al-Jawaad (AS).
She was from the family of Mariyah Al-Qibtiyyah the wife of the Prophet Muhammad (SAWA) who gave birth to his son Ebrahim.
We have many Hadeeths praising her.
She is known as Sabeeka al-Noobiyyah (Sabeeka of Nooba which is Egyptian Africa).
She is also known by other names like Khaizaraan and Rayhana.
The meaning of Sabeeka in Arabic is a piece of Gold.
It is good to keep this name for newborn girl. It is already used as name for thousands of Muslim females.