Sayyiduna Abu Hurayrah (may Allah be pleased with him) narrates: the Prophet (peace and blessings be upon him) said: "Whoever sees some flaw in his brother's religion and then conceals it, that will be a good deed for him on the Day of Resurrection."
Al-Tabarani recorded it in al-Mu'jam al-Awsat. Its chain contains Abu Salih al-Khuzi, who is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الحدود والديات / 10479