While speaking to us, Hoca (Shaykh Mustafa Azami, Allah have mercy on him) told us that when he was student at Al-Azhar, he once went to get some milk. On the wall of the milk seller’s shop, it was written with calligraphy: “The one who cheats, he is not from one of us.” This is taken from a hadith. But the milk seller was adding water to the milk in front of this hadith on his wall.

Everyone laughed upon hearing this.

But Hoca added, “You all too, when you reach the class five minutes late, when you do not prepare well, when you waste time in empty talk during the class, you too fall to the level of the man adulterating milk with water.” Everyone was taken back upon hearing this. A pin drop silence followed.

Till today, I’ve not forgotten those words. I try to fulfill the rights of the class lesson in its true sense. I remind myself that whenever I go late to class, or if I don’t prepare myself well, I fall to the level of the man mixing milk with water.

https://www.ilmgate.org/remembering-shaykh-mustafa-azami-a-talk-by-dr-recep-senturk/