An-Nu`man bin Bashir (May Allah be pleased with them) reported: The Prophet (PBUH) said, "Du`a (supplication) is worship.''
[Abu Dawud].

Commentary: What is prayer but an expression of one's humbleness and helplessness before Allah. The expression of one's weakness, inferiority and lowliness before the Infinite Power and Might of Allah is in fact the essence of worshipping Him. For this reason, prayer has been regarded as the essence of worship. Thus, prayer is reserved for Him Alone and it should not be addressed to anyone else in any case. Al-Qadi `Iyad said that Du`a is that act of worship which alone deserves to be referred to as `Ibadah, or worship, because when one observes it, one in fact shows drawing near to Allah, utter dedication to Him and rejection of all that He does not like and approve.