Answered by Shaykh Faraz Rabbani
Is it considered bad adab to write notes (in pen/ pencil) in fiqh books/ Quran/ hadith books etc? What about highlighting?
Walaikum assalam wa rahmatullah,
In the Name of Allah, Most Merciful and Compassionate. May His blessings and peace be on His Beloved Prophet, the best of creation, and his family, companions, and followers.
There is nothing wrong with writing notes in books, or to highlight them. If it helps one study, it would be praiseworthy.
However, one should not write within the Qur’an nor highlight it. If one writes in the margin, one should only do so with the utmost caution, lest one’s notes be misunderstood as being commentary by another reader.
And Allah alone gives success.