Our Shaykh, is the following hadth true, or is it from the books of the Shias?
“Surely, a river of milk flows in heaven, for Ali, Hussain, and Hasan, and all those who have love for these three shall enter the garden with no misery.”

All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger. 

We could not find any such hadeeth or report, be it authentic, weak, or even fabricated, in the books and references available to us. This wording may have no basis in the Sunnah and was merely fabricated by some liars and advocates of extreme practices related to ‘Ali and his descendants. Al-Mugheerah, may Allah be pleased with him, narrated that the Prophet, sallallahu ‘alayhi wa sallam, said, “Indeed, a lie upon me is not like a lie upon anyone else, for whoever lies upon me intentionally, then he shall take his seat in Hellfire.” [Al-Bukhari and Muslim]

There are many authentic ahaadeeth that underline the great virtues and merits of ‘Ali, Al-Hasan, and Al-Husayn, may Allah be pleased with them, and that suffice us and leave us without a need for such fabricated reports. Loving them entails following their example in terms of their sound practices and their love for the Companions of the Prophet, sallallahu ‘alayhi wa sallam, on the top of whom are Abu Bakr and ‘Umar, may Allah be pleased with them, and with them all the Companions.

Allah knows best.