The Sufficient (Vol 4) · Hadith 489 (#Ḥadīth #3)
Chapter 45 | Children’s Fasting and When They Owe Fasting
3ـ أَحْمَدُ بْنُ مُحَمَّدٍ عَنْ عُثْمَانَ بْنِ عِيسَى عَنْ سَمَاعَةَ قَالَ سَأَلْتُهُ عَنِ الصَّبِيِّ مَتَى يَصُومُ قَالَ إِذَا قَوِيَ عَلَى الصِّيَامِ.
3. Ahmad ibn Muhammad from has narrated from ‘Uthman ibn ‘Isa from Sama‘ah, who has said the following: “I once asked abu ‘Abd Allah , about a child when he is required to fast. He (the Imam) said, ‘When he is able to fast he must fast.’”
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).