Suhayb reported: The Messenger of Allah, peace and blessings be upon him, said, “Wondrous is the affair of a believer, as there is good for him in every matter; this is not the case for anyone but a believer. If he experiences pleasure, he thanks Allah and it is good for him. If he experiences harm, he shows patience and it is good for him.”
Source: Ṣaḥīḥ Muslim 2999
Grade: Sahih (authentic) according to Muslim
عَنْ صُهَيْبٍ قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ عَجَبًا لِأَمْرِ الْمُؤْمِنِ إِنَّ أَمْرَهُ كُلَّهُ خَيْرٌ وَلَيْسَ ذَاكَ لِأَحَدٍ إِلَّا لِلْمُؤْمِنِ إِنْ أَصَابَتْهُ سَرَّاءُ شَكَرَ فَكَانَ خَيْرًا لَهُ وَإِنْ أَصَابَتْهُ ضَرَّاءُ صَبَرَ فَكَانَ خَيْرًا لَهُ
2999 صحيح مسلم كتاب الزهد والرقائق باب المؤمن أمره كله خير