The following comment was by y not.
When I tried to add the link, the post disappeared. Luckily, I kept a copy.
Googled ‘Arahant at 7 years old’ and got this for starts. I do not know whether there is more.
At seven years old
I received ordination.
I bear my final body—
oh, the excellence of the teaching!
I was only seven years old
and had just gone forth..
“he is Anuruddha’s novice,
assured in psychic powers.
Made a thoroughbred by a thoroughbred,
made good by the good,
educated and trained by Anuruddha,
who has completed his task”…
Having attained ultimate peace
and witnessed the unshakable,
that novice Sumana has the wish:
‘May no-one find me out!
P.S. I just added the links to the references that y not provided.
Thank you, y not!