It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) placed his hand on the head of Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) and said: "O Allah! Grant him wisdom, and teach him interpretation (ta'wil, deep understanding of the Qur'an)." And he placed his hand on his chest, and Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) felt its coolness in his back. Then he said: "O Allah! Fill his chest with wisdom and knowledge." After that, he never felt within himself any need to ask anyone among the people (about anything), and he remained the foremost scholar of this Ummah until Allah took him to Himself.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10539