The vastness of knowledge

It is narrated from a man of Banu Abs that he said: I was with Sayyiduna Salman al-Farisi (may Allah be pleased with him), and when we passed by the river Tigris he said: "O brother of Banu Abs, dismount and drink." So I dismounted and drank. Then he said again: "Dismount and drink." So I dismounted again and drank. After that he asked me: "O brother of Banu Abs, what has your drinking taken away from the water of the Tigris?" I said: "What could my drinking possibly take away from the water of the Tigris?" He said: "Knowledge is exactly like this; it never runs out, so be sure to take from it what can benefit you."
Abu Ya'la recorded it in his Musnad; one narrator in its chain is unnamed, but its meaning is established by other authentic hadith and reports.

It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both), and the narrator thinks that he narrated it marfu' from the Prophet (peace and blessings be upon him), that he (peace and blessings be upon him) said: "There are two greedy ones whose thirst is never quenched, and neither of them ever reaches the end of his craving: one who is extremely greedy in seeking knowledge, who is never satisfied in his thirst for knowledge; and the other who is greedy for wealth and riches, who is never content in his lust for money."
I (Ibn Hajar) say: Layth bin Abi Sulaym is a da'if (weak) narrator; however, it has a shahid (supporting report) from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) with al-Tabarani, and from Sayyiduna Anas (may Allah be pleased with him) with Ibn Adi, and both of them narrated it marfu'. Also, this report is transmitted from Imam al-Hasan al-Basri in mursal form, and its chain up to Imam al-Hasan al-Basri is sahih (authentic).