Arifbillah Dr. Abdul Hayy Arifi relates that in the last years of his life Hakim al-Umma Shaykh Ashraf Ali Thanawi (Allah have mercy on them) used to say,

‘At 80 years of age I have come to the conclusion that dua (supplication) is the most superior form of worship (i’badah).”

Explaining it further Hazrat Arifi ra said this because in dua one has a sincere concentrated attention(tawajuh ilal Allah) and turning towards Allah SWT(ruju’ ilal Allah).

Also it is a manifestation of one’s slavehood(a’bdiyat) and total dependence  (muhtaj ).’

Jawahir Hakim al-Umma ra