Complex sentence: At 183 AD, when the Imamah was transferred to Ali al-Ridha, Imam Musa al-Kadhim was a prisoner for many years and therefore promotion of shia's teaching was stopped.
Split into simpler sentences: At 183 AD, Imamah was transferred to Ali al-Ridha. At that time Imam Musa al-Kadhim was a prisoner for many years and therefore promotion of shia's teaching was stopped.