The Prophet ﷺ said, "Supplication is worship," then he recited, "Your Lord has said, 'Call upon Me, I will respond to you'" [Ghafir 40:60].
حدثنا حفص بن عمر حدثنا شعبة عن منصور عن ذر عن يسيع الحضرمي
عن النبي ﷺ قال الدعاء هو العبادة {قال ربكم ادعوني أستجب لكم}
Its isnad is sahih. Tirmidhi transmitted it in the chapter on the tafsir of the Quran, section on Surah Baqarah, 2969, and Ibn Majah, hadith 3828, from the hadith of Dharr bin Abdullah Hamdani, with the same chain. Tirmidhi said, hasan sahih. Ibn Hibban graded it sahih, hadith 2396, as did Hakim, 1/490, 491, and Dhahabi agreed with him.