Is the saying: "Do not ask your brother about his fasting. For if he is fasting, he will rejoice, and if he is not, he will be saddened, and both are ostentation," correct, and who said it?

The attribution of the aforementioned statement to any of the Salaf (pious predecessors) has not been substantiated. Scholars have discussed the joy and delight in obedience, and that it does not contradict sincerity if the servant is sincere and does not strive to show it off, citing the words of Ibn Aqil: "Self-admiration is not joy, and joy does not detract from acts of obedience, because it is the soul's delight in the obedience of the Lord, عز وجل (the Mighty and Majestic)." Imam Al-Ghazali also mentioned in Ihya’ ‘Ulum al-Din that delight in obedience is divided into praiseworthy and blameworthy. The praiseworthy is the joy in Allah's favor, His concealing of ugly deeds, and His manifesting of beautiful ones, inferring from this one's state in the afterlife, loving for people to emulate him, and his joy at people's love for those who are obedient. The blameworthy is the joy whose cause is a desire for status in people's hearts, their praise, and their veneration.