Du'a
Du'a is considered the most noble act in the sight of Allah. Prophet Muhammad (Sal Allahu Alayhi Wa Sallam) said...
"There is nothing more noble in the sight of Allah than Du'a."
Du'a is also considered the best form of worship. It is a direct link between a human being and Allah. Prophet Muhammad (Sal Allahu Alayhi Wa Sallam) said...
"The best form of worhip is Du'a."
And your Lord says...
"Call on Me; I will answer your (Prayer): but those who are too arrogant to serve Me will surely find themselves in Hell - in humiliation!" (Quran, Surah Al-Ghafir, 40:60)