My beloved friend instructed me to observe three things: never to sleep without praying witr, to fast three days of every month, and never to abandon the two units of the forenoon prayer.
حدثنا معتمر عن ليث عن مجاهد وشهر
أوصاني خليلي بثلاث أن لا أنام إلا على وتر وأن أصوم ثلاثة أيام من كل شهر وأن لا أدع ركعتي الضحى
Its isnad is sahih via the route of Mujahid, and hasan via the route of Shahr. This hadith has already appeared at 2138 and 9878.10399m1 - Abdullah said, "I found these two hadiths in my father's book, in his own handwriting. He said, Muhammad bin Abdullah Ansari narrated to us. Muhammad bin Amr narrated to us, from Abu Salama, from Abu Hurairah, who said, 'The Messenger of Allah ﷺ said, "Do not precede the month" - meaning Ramadan - "by a day or two, unless it coincides with a fast that one of you was already observing."'"Sahih (10399m1). Its isnad is sahih. Abdullah bin Ahmad relates it from a written source he found, but the hadith has already appeared at 9618.10399m2 - "Fast upon sighting it, and break the fast upon sighting it. If it is obscured from you, then count thirty days, then break the fast."Sahih (10399m2). Its isnad is sahih. This too is from a written source he found, and it has already appeared at 1931 and 9520.