Is it permissible to accept wakaf from non-Muslims?
Alhamdulillah, praise and gratitude to Allah SWT for His countless blessings for us all. Praise and salutations to our beloved Prophet Muhammad PBUH, his family, companions and all those who follow his footsteps until the Last Day.
Wakaf according to 4th Edition of Kamus Dewan is something given for public use or something dedicated to the needs related to the religion of Islam. For example, wakaf land is reserved for religious purposes such as to be made as a graveyard, build a mosque and others.
According to Ibn Manzur, wakaf originates from the Arabic word waqf which is a derivative (masdar) from the verb waqafa. It has various meanings following the purpose and usage of the sentence itself. Lexically, waqf means stop (السكن), prevent (المنع) and impede (الحبس). 
In terms of the usage of the terminology, wakaf is impeding something from being owned and that its benefits are to be donated. Hence, the ownership of the asset changed to the ownership of Allah SWT. 
Dr Wahbah al-Zuhayli stated, wakaf is halting a permanent immovable asset for charitable purposes and it is handed over to certain chosen parties with the hope to get closer to Allah SWT. 
Islam greatly encourages wakaf amongst Muslims themselves. The terminology of the word wakaf means impeding a property from which its physical value doesn’t decrease and can be used or benefit from by handing over its ownership to a user (someone) who is permissible and exist. 
Answering the above question, the ruling of accepting wakaf property from non-Muslims is permissible and valid. This include wakaf to be given to mosques even though the intention is not to get closer (taqarrub) to Allah SWT. 
This matter is based on the hadith from Anas bin Malik RA, the Prophet PBUH said:
إِنَّ اللَّهَ لاَ يَظْلِمُ مُؤْمِنًا حَسَنَةً يُعْطَى بِهَا فِي الدُّنْيَا وَيُجْزَى بِهَا فِي الآخِرَةِ وَأَمَّا الْكَافِرُ فَيُطْعَمُ بِحَسَنَاتِ مَا عَمِلَ بِهَا لِلَّهِ فِي الدُّنْيَا حَتَّى إِذَا أَفْضَى إِلَى الآخِرَةِ لَمْ تَكُنْ لَهُ حَسَنَةٌ يُجْزَى بِهَا
“Verily, Allah does not treat a believer unjustly in regard to his virtues. He would confer upon him (His blessing) in this world and would give him reward in the Hereafter. And as regards a non-believer, he would be made to taste the reward (of virtue in this world) what he has done for himself so much that when it would be the Hereafter, he would find no virtue for which he should be rewarded.” 
According to the above hadith, a non-Muslim will receive the rewards in this world appropriate with the wakaf or good that he gives. However, he will not receive any good or rewards in the hereafter. 
According to the question, we find that it is permissible to accept the wakaf from non-Muslims even in matters involving a mosque. The reason is non-Muslims are also included as those who have a right to donate. Hence, accepting wakaf property from non-Muslims is permissible.
Hopefully, this explanation it will give is a true understanding in our lives to become better every day. Amin.
 See al-Fiqh al-Islami wa Adillatuh, 8/155
 See Mughni al-Muhtaj, 2/376
 See Hasyiah al-Baijuri, 2/80
 See al-Fiqh al-Manhaji, 3/183