I am expecting the birth of my son soon and want to name him "Wali." I know "Al-Wali" is one of Allah's 99 names, and "Abdul" should be added before some (but not all) of these names when naming a person. Can I name my son "Wali" or should it be "Abdul Wali"? Is adding "Abdul" before "Wali" mandatory?
There are some beautiful names of Allah Ta'ala which the Quran and Hadith have used for other people, this will be permissible, such as the name Rahim (merciful), Ra'uf (compassionate), Rashid (rightly guided), Shakur (Most Thankful), Wajid (Perceiver), Ali (exalted), Kareem (noble), Aziz (powerful) etc. These names have shared meanings which can be intended for both people and Allah Ta'ala.
There are also names which are exclusively for Allah Ta'ala from the Quran and Hadith, then this will not be used for other people, such as Al-Rahman (compassionate), Al-Quddus (pure), Al-Jabbar (mighty), Al-Tawwab (forgiver), Al-Samad (Eternal), Al-Qahhar (Subduer), Al-Qadir (Capable), Al-Khaliq (creator), Al-Razzaq (provider) etc. It is Haram and impermissible to call a human being with these names without the prefix 'Abd' attached to it.
So the above name ‘Wali’ (guardian or protector) can be kept with out adding ‘Abd’ like Abdul Wali before it.
التسمية باسم يوجد في كتاب الله كالعلي والكبير والرشيد والبديع جائزة لأنه من الأسماء المشتركة ويراد في حق العباد غير ما يراد في حق الله تعالى كذا في السراجية
(فتاوي عالكييرية ٥/٣٦٢)