All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
This hadeeth was quoted by Ad-Daylami in his book Al-Firdaws bi Ma’thoor Al-Khitaab without any chain of narrators. As-Suyooti and others also quoted this hadeeth from him, but we have not come across any scholar from among those who are specialized in classifying the ahaadeeth who classified it as authentic or weak.
There is another hadeeth close to this one in meaning/wording; it was narrated by Ibn ‘Umar who said, “The Prophet said, 'The best act of worship is Fiqh (seeking religious knowledge), and the best of religion is piety.'” Al-Munthiri said, “This hadeeth was reported by At-Tabaraani in his three volumes, and its chain of narrators include Muhammad ibn Abi Layla.”
Al-Albaani classified this hadeeth as weak in Dha’eef At-Targheeb wat-Tarheeb.
There is another hadeeth, classified by Shaykh Al-Albaani as saheeh (sound), that was narrated by Huthayfah ibn al-Yamaan who related that the Prophet said, “The excellence of knowledge is better than the excellence of worship, and the best of your religion is piety.”
Al-Munthiri said, “This hadeeth was reported by At-Tabaraani in Al-Awsat, and it was reported by Al-Bazzaar with a good chain of narrators.”
Allaah knows best.