This hadith has been narrated on the authority of Musa b. `Uqba with the same chain of transmitters and he did not make a mention of:"Be happy".
وَحَدَّثَنَاهُ حَسَنٌ الْحُلْوَانِيُّ، حَدَّثَنَا يَعْقُوبُ بْنُ إِبْرَاهِيمَ بْنِ سَعْدٍ، حَدَّثَنَا عَبْدُ الْعَزِيزِ، بْنُ الْمُطَّلِبِ عَنْ مُوسَى بْنِ عُقْبَةَ، بِهَذَا الإِسْنَادِ وَلَمْ يَذْكُرْ " وَأَبْشِرُوا " .
Muslim
Characteristics of the Day of Judgment, Paradise, and Hell • Hadith 76