The Prophet salallahu alaihi wassalaam made two notable du’a for Abdullah ibn Abbas :
O Allah give this young boy a deep understanding of this religion and grant him the knowledge of the tafseer of the Quran. (Abdullah grew to be known as the jurist of the ummah and has the deepest knowledge of the revelations and tafseer).

O Allah grant this child wisdom. (Abdullah ibn Abbas grew to become such a wise and mature person).

Lesson : Do not underestimate a dua of a pious person. Most powerful prayer is when you pray for someone without them knowing that you have prayed for them.