This is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both), and the Messenger of Allah (peace and blessings be upon him) said: "When I command you to do something, do of it as much as you are able."
Sayyiduna Abu Hurayrah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "Leave me as long as I leave you. Those before you were destroyed only because of their many questions and their disagreeing with their prophets. So when I forbid you from something, avoid it, and when I command you to do something, do of it as much as you are able."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8214