Arabic text
عن أبي هريرة رضي الله عنه عن النبي صلى الله عليه وسلم قال: «لَيْسَ شَيْءٌ أَكْرَمَ عَلَى اللهِ تَعَالَى مِنَ الدُّعَاءِ».
Translation
Abu Hurayrah (may Allah be pleased with him) reported: The Prophet (may Allah's peace and blessings be upon him) said: "Nothing is more honorable in the sight of Allah Almighty than supplication."
Explanation
The Prophet (may Allah's peace and blessings be upon him) pointed out that no act of worship is more virtuous in the sight of Allah Almighty than supplication. This is because supplication comprises recognition of Allah's self-sufficiency and the servant's helplessness and need of his Lord.
Source: HadeethEnc.com