What is the meaning of Allah's name, Al-Shahid?

"Al-Shaheed" (The Witness) is the one who is truthful in His testimony, the one from whose knowledge nothing is absent, the Present, and the one who will bear witness against creation on the Day of Judgment, and all His creation points to His Oneness.

"Al-Shaheed" (The Witness), "Al-Khabeer" (The All-Aware), and "Al-Alim" (The All-Knowing) all refer to knowledge; "Al-Shaheed" pertains to apparent matters, "Al-Khabeer" to hidden matters, and "Al-Alim" encompasses both.

And Allah Almighty is Shaheed because He knows things and their realities with an evident knowledge, and nothing is hidden from Him. He is the Witness for the oppressed against the oppressor, and the One who is aware of everything, hearing and seeing every sound and existing thing; His knowledge encompasses everything, and He bears witness for and against His servants concerning what they have done.