ENOfficial
It was narrated that Abu Al-Hawra' As-Sa'di said: "I said to Al-Hasan bin 'Ali, may Allah be pleased with him: 'What did you memorize from the Messenger of Allah (ﷺ) ?' He said: I memorized from him: 'Leave that which makes you doubt for that which does not make you doubt.'"
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنَا مُحَمَّدُ بْنُ أَبَانَ، قَالَ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ إِدْرِيسَ، قَالَ أَنْبَأَنَا شُعْبَةُ، عَنْ بُرَيْدِ بْنِ أَبِي مَرْيَمَ، عَنْ أَبِي الْحَوْرَاءِ السَّعْدِيِّ، قَالَ قُلْتُ لِلْحَسَنِ بْنِ عَلِيٍّ رضى الله عنهما مَا حَفِظْتَ مِنْ رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ حَفِظْتُ مِنْهُ " دَعْ مَا يَرِيبُكَ إِلَى مَا لاَ يَرِيبُكَ " .
sunnah.com