[16].Surah An-Nahl [The Bees] : Ayat 8-9

Ayat 8. And (He has created) horses, mules and donkeys, for you to ride and as an adornment. And He creates (other) things of which you have no knowledge.

Ayat 9. And upon Allâh is the responsibility to explain the Straight Path (i.e. Islâmic Monotheism for mankind i.e. to show them legal and illegal, good and evil things, etc. so, whosoever accepts the guidance, it will be for his own benefit and whosoever goes astray, it will be for his own destruction), but there are ways that turn aside (such as Paganism, Judaism, Christianity, etc.). And had He willed, He would have guided you all (mankind). 

Hazrat Muawiyah (May Allah be pleased with him) reported: The Messenger of Allah  [SAWW](PBUH) said, "When Allah wishes good for someone, He bestows upon him the understanding of Deen.''

[Al-Bukhari 01, Chapter 03, Hadith # 071]. 

Lesson : as mentioned above in Surah An-Nahl Ayat 9. "and has He willed, He would have guided you all (mankind).

Knowledge and understanding of Deen (religion) here stands for the understanding of the Qur'an and Hadith, religious injunctions, and knowledge of the lawful and the unlawful. This Hadith highlights the excellence of knowledge and the fact that it is a sign of Allah's Help to the person who possesses it and acts upon it.