Sahl b. Sa’d (radiyallaahu ‘anhu) said: Allaah’s Messenger (salallaahu ‘alaihi wassallam) said:
“Me and the sponsor of the orphan will be like this in Paradise.” Then he indicated with his index and forefinger, separating between them. (Al-Bukhaaree, no. 5304).
Shaikh Muhammad b. Saalih al-‘Uthaimeen (rahimahullaah) said:
The limit at which one remains an orphan finished at adolescence (adulthood). So when a child reaches adulthood then he is no longer an orphan. And before the age of adolescence, he remains an orphan if his father has passed away. And if it is the case that his mother has passed away whilst his father is alive, then he is not an orphan.
(Explanation of Riyaadus-Saaliheen, 1/645)