ENOfficial
Sa'id b. al-‘As said he asked Abu Musa and Hudhaifa how God’s Messenger said “God is most great” on the day of sacrifice and of the breaking of the fast. Abu Musa said he uttered it four times as he did at funerals and Hudhaifa said that that was correct. Abu Dawud transmitted it.
Source: sunnah.com
Other translations
Arabic
وَعَنْ سَعِيدِ بْنِ الْعَاصِ قَالَ: سَأَلْتُ أَبَا مُوسَى وَحُذَيْفَةَ: كَيْفَ كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يُكَبِّرُ فِي الْأَضْحَى وَالْفِطْرِ؟ فَقَالَ أَبُو مُوسَى: كَانَ يُكَبِّرُ أَرْبَعًا تَكْبِيرَهُ على الجنازه. فَقَالَ حُذَيْفَة: صدق. رَوَاهُ أَبُو دَاوُد
sunnah.com