Tafsir of Al Imran 3:138

هذا بيان للناس

This is a plain statement for mankind, meaning, the Qur'an explains the true reality of things and narrates how the previous nations suffered by the hands of their enemies.

وهدى وموعظة

And a guidance and instruction, for the Qur'an contains the news of the past, and,

هدى

(guidance) for your hearts.

وموعظة للمتقين

and instruction for the Muttaqin. to discourage committing the prohibited and forbidden matters. Allah comforts the believers by saying,