كتاب صفة القيامة والجنة والنار
52  
Characteristics of the Day of Judgment, Paradise, and Hell
(17)
Chapter: No One Will Enter Paradise By Virtue Of His Deeds, Rather By The Mercy Of Allah, Exalted Is He
(17)
باب لَنْ يَدْخُلَ أَحَدٌ الْجَنَّةَ بِعَمَلِهِ بَلْ بِرَحْمَةِ اللَّهِ تَعَالَى ‏‏
Sahih Muslim 2818 b

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 ‏"‏ ‏.‏
Reference : Sahih Muslim 2818b
In-book reference : Book 52, Hadith 76
USC-MSA web (English) reference : Book 39, Hadith 6771
  (deprecated numbering scheme)