[Q]: Who is Jibrāʾīl (Gabriel)?

[A]: Do you not know who Jibrāʾīl (Gabriel) is? Jibrāʾīl is the best of the Angels, the trustworthy one who was entrusted by Allāh with the revelation.

نَزَلَ بِهِ الرُّوحُ الْأَمِينُ

Which the trustworthy Ruḥ [Jibrāʾīl] has brought down
[Sūrah al-Shuʿarāʾ, 26:193]

This means that the Qurʾān was sent down by the trustworthy spirit, who is Jibrāʾīl (عليه السلام)

عَلَىٰ قَلْبِكَ

Upon your heart (O Muḥammad)
[Sūrah al-Shuʿarāʾ, 26:194]

Meaning upon the heart of the Messenger(صلى الله عليه وسلم), so he is the trustworthy spirit (عليه السلام) and the chief of Angels.

Source: Shaykh Fawzān’s website.
Translated by: Munīb al-Ṣumālī.