What does "and He taught Him of what He willed" refer to?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. It refers to the craft of making armour.
2. It refers to the Psalms (Zabūr).
3. It refers to the speech of birds.