Hadith #170 (Jami' al-Tirmidhi)
Book: The Book on Salat (Prayer)
Narrator(s): Abdullah bin 'Umar bin Hafs bin 'Asim عبد الله بن عمر بن حفص بن عاصم, al-Fadl bin Musa al-Synany الفضل بن موسى السيناني, al-Husain bin Hryth الحسين بن حريث, al-Qasim bin Ghnam al-Ansari القاسم بن غنام الأنصاري البياضي المدني

“The Prophet was asked: ‘Which deed is the best?’ So he said: ‘Salat in the beginning of its time.'”

Source: https://parallelquran.com/hadith/jami-al-tirmidhi-170/