Sunan Abi Dawud, Hadith 4386 ⓘ
A similar tradition has also been transmitted by al-A’mash through a different chain of narrators. He also said : “.... Till he reaches puberty, and a lunatic till he is restored to consciousness.” ‘Umar then began to utter: Allah is most great.
حَدَّثَنَا يُوسُفُ بْنُ مُوسَى، حَدَّثَنَا وَكِيعٌ، عَنِ الأَعْمَشِ، نَحْوَهُ وَقَالَ أَيْضًا حَتَّى يَعْقِلَ . وَقَالَ وَعَنِ الْمَجْنُونِ حَتَّى يُفِيقَ . قَالَ فَجَعَلَ عُمَرُ يُكَبِّرُ .
also referenced under: Hadith 4400 (DarusSalam)