Question: Is it permitted to prostrate to the graves of Imams (a.s)?
Answer: As we have explained in the reply to one question prostration is restricted only for the Almighty Allah and except for Him, whoever it might be, it is not allowed. And if some people do it, it is due to their unfamiliarity of the rules of religion and they should be explained that it is not permitted to prostrate to the Imam or the grave of the Imam.
Also, it should be remembered that prostration on tablets of soil prepared from the soil of the graves of some holy personalities is not the prostration of these holy ones. Rather according to the tradition of Islamic leaders, prostrating to Allah with intention of more humility we must touch our head on the ground or that which grows out of the earth (and not used in eating or it is not a minerals). And the soil of Imam Husain's (a.s) grave (Khak-e-Shifa) is also that pure soil on which Imam Husain (a.s) camped for revival of Islam. On the basis of this it has attained a great merit.
Especially when a person prostrate on a tablet of the soil of Kerbala, it renews for him the remembrance of the sacrifice of Imam Husain Ibn Ali Ibn Abi Talib (a.s). And it invites the pure souls to follow the lofty exemplar and makes their feelings of sacrifice and faith stronger.