ENOfficial
Mu‘adh told of hearing God’s Messenger say, “The man who withholds goods is evil. If God lowers prices he is grieved, and if He raises them he is happy.” Baihaqi transmitted it in Shu'ab al-lman and Razin in his book.
Source: sunnah.com
Other translations
Arabic
وَعَنْ مُعَاذٍ قَالَ: سَمِعْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ: " بِئْسَ الْعَبْدُ الْمُحْتَكِرُ: إِنْ أَرْخَصَ اللَّهُ الْأَسْعَارَ حَزِنَ وَإِنْ أَغْلَاهَا فَرِحَ ". رَوَاهُ الْبَيْهَقِيُّ فِي شُعَبِ الْإِيمَانِ وَرَزِينٌ فِي كِتَابِهِ
sunnah.com