Is a Muslim obligated to convey everything he knows about the religion, even if he is not asked about it, and is supplication sufficient for him if he is unable to inform others?

If a person is obligated to convey knowledge and teach the ignorant, but is unable to do so, then he is excused and incurs no sin. However, if the failure to convey knowledge is merely due to shyness, then he sins by neglecting it.