Praise be to Allaah.

Perhaps the hadeeth referred to in the question is that which was narrated by ‘Uthmaan ibn ‘Affaan (may Allaah be pleased with him), and says that the Prophet (peace and blessings of Allaah be upon him) said: “The best of you is the one who learns the Qur’aan and teaches it.” Narrated by al-Bukhaari (5027). 

There is a great deal of encouragement to learn to read Qur’aan, both in the Qur’aan and Sunnah. There is also encouragement to learn how to read. The Holy Qur’aan is the only book that the Muslims read at the beginning of Islam, so learning to read and write started with learning the Holy Qur’aan. Indeed the command to learn to read came with the first word of the Revelation that came to the Messenger of Allaah (peace and blessings of Allaah be upon him), when Allaah said (interpretation of the meaning):  

“Read! In the Name of your Lord Who has created (all that exists).

2. He has created man from a clot (a piece of thick coagulated blood).

3. Read! And your Lord is the Most Generous.

4. Who has taught (the writing) by the pen.

5. He has taught man that which he knew not”

[al-‘Alaq 96:1-5]. 

Knowledge spread and ignorance decreased as the result of learning to read and write the Qur’aan and understand its meanings. 

But if what is meant is another hadeeth in which it says that Allaah loves those who learn to read in general, then we could not find this wording in any of the books of Sunnah.