Jami` at-Tirmidhi 534
جامع الترمذي#534SahihUbaidullah bin Abdullah bin Utbah narrated:"Umar bin Al-Khattab asked Abu Waqid Al-Laithi what Allah's Messenger would recite during Al-Fitr and Al-Adha, so he said: 'He would recite: Qaf, By the Glorious Quran and the Hour has drawn near, and the moon has been cleft asunder
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Bashar Awad MaaroufHasan Sahih
Zubair Ali ZaiSahih Muslim
In-book reference: 5:5