Obligatory duties for those who are deaf and mute

Shaykh ‘Abd al-‘Azeez ibn ‘Abd-Allaah ibn Baaz explained that the child who
is deaf and mute, when he reaches the age of puberty, is considered to be
accountable and expected to fulfil the obligations of prayer, etc. He added
that he may be taught what he needs to know by means of writing or signing,
because of the general meaning of the shar’i evidence which indicates that
these obligations apply to everyone who reaches the age of puberty and is of
sound mind. Puberty is reached at the age of fifteen, or when maniy
(discharge) is emitted as a result of feeling desire in a dream (“wet
dream”) or otherwise, and when coarse hair grows around the private parts.
In the case of women, there is a fourth sign of puberty, which is the onset
of menstrual periods.  
The shaykh called upon the guardian of the one who is deaf or mute to pay
zakaah and fulfil other financial obligations on his behalf. He also has to
teach him what he does not know by all possible means so that he will
understand what Allaah requires of him and what Allaah has forbidden for
him. 
The shaykh quoted as evidence the words of Allaah (interpretation of the
meaning):
“So keep your duty to Allaah and fear Him as much as you can”
[al-Taghaabun 64:16]
And the hadeeth of the Prophet (peace and blessings of Allaah be upon him):
“If I command you to do a thing, then do as much of it as you can.” 
And the shaykh explained that the accountable person who cannot hear or
speak, or who becomes unable to hear or speak, should fear Allaah and keep
his duty towards Him as much as he can by doing that which is enjoined upon
him and abstaining from that which is haraam. He should try to learn as much
of the religion as possible, by watching, writing and signing, so that he
may understand what is required.