[Machine] The Messenger of Allah ﷺ heard a man calling out in his slogan: "O Haram, O Haram." So the Messenger of Allah ﷺ said: "O Halal, O Halal." This hadith is deemed authentic according to the conditions of both Al-Bukhari and Muslim (the two acknowledged scholars of hadith). It was narrated by a man named Muhammad ibn Kathir from Thawri, Abdullah ibn Mughaffal Al-Muzani.
سَمِعَ رَسُولُ اللَّهِ ﷺ رَجُلًا يُنَادِي فِي شِعَارِهِ يَا حَرَامُ يَا حَرَامُ فَقَالَ رَسُولُ اللَّهِ ﷺ «يَا حَلَالُ يَا حَلَالُ» صَحِيحٌ عَلَى شَرْطِ الشَّيْخَيْنِ عَلَى الْإِرْسَالِ «وَإِذَا الرَّجُلُ الَّذِي لَمْ يُسَمِّهِ مُحَمَّدُ بْنُ كَثِيرٍ عَنِ الثَّوْرِيِّ عَبْدِ اللَّهِ بْنِ مُغَفَّلٍ الْمُزَنِيِّ»