Tafsir of Ta-Ha 20:19

He said: An inception built upon a question to which the mind is drawn, as if it were said: "So what did Allah—Mighty and Majestic is He—say?" Thus, it was said: "He said: 'Throw it down, O Moses.'"

[He said: "Throw it down, O Moses"] in order that you may see of its state what you will see. Al-ilqa' (throwing) is casting something onto the ground, and from it is His saying: "And she cast down her staff, and the place of exile settled with her," just as the traveler is comforted by the return. The repetition of the call is for the sake of increased alerting and attention to the matter of the staff. That the speaker of this is Allah—the Exalted—is what is apparent. Some have claimed that it is permissible for the speaker to be an angel by the command of Allah—the Exalted—but this is extremely far-fetched.