TIRMIDHI 3371:
from Anas b. Mālik —
the Prophet said: “The supplication is the essence of worship.”
الترمذي ٣٣٧١:
عن انس بن مالك —
عَنِ النَّبِيِّ ﷺ قَالَ الدُّعَاءُ مُخُّ الْعِبَادَةِ