Bismillah hir rahman nirrahim
Alhamdulillah

Nu’man ibn Bashir (Radi Allahu Anhu) se rivayat hai ki RasoollAllah (Sallallahu Alaihi Wa sallam) ne farmaya: ‘Dua Ibadat hai, aur tumharey Rab ka farman hai (Quran 40 : 60) mujhse dua karo mein Qubul karunga.’

[Sunan Abu Dawud, Vol 1, 1466]

Hadith English:
Narrated An-Nu’man ibn Bashir May Allah be Pleased with Him: The Prophet (peace and blessing be upon him) said: Supplication (du’a’) is itself the worship. (He then recited Quran 40 : 60) “And your Lord said: Call on Me, I will answer you”

[Sunan Abu Dawud, Vol 1 , 1474]