It is narrated from Sayyidah Umm Farwah (may Allah be pleased with her); she said: The Messenger of Allah (peace and blessings be upon him) said: "The deed most beloved to Allah, the Mighty and Majestic, is offering the prayer at the beginning of its time."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21671