Is it permissable for a scholar to recieve govermental salary?

The Holy Quran in different verses says that the Prophet(PBUH) did not ask any wage for Islam. For example: > لِكَ الَّذِي يُبَشِّرُ اللَّـهُ عِبَادَهُ الَّذِينَ آمَنُوا وَعَمِلُوا > الصَّالِحَاتِ ۗ قُل لَّا أَسْأَلُكُمْ عَلَيْهِ أَجْرًا إِلَّا > الْمَوَدَّةَ فِي الْقُرْبَىٰ ۗ وَمَن يَقْتَرِفْ حَسَنَةً نَّزِدْ لَهُ > فِيهَا حُسْنًا ۚ إِنَّ اللَّـهَ غَفُورٌ شَكُورٌ > > This is the glad tidings that Allah gives to His worshipers, who > believe and do good works. Say: '**For this I ask of you no wage** except > the love of the (Prophet's) relatives. We will add good to whosoever > gains a good deed. Allah is the Forgiving and the Thanker' > (42:23 ) Also Imam Ali a.s. did not receive any governmental wage for himself and always had his own business (farming) even when he was the Caliph. Also Salman Farsi (a.s.) one of the great Sahabas of the Prophet (SAWW) did not take any governmental wage for himself when he was the governor of Madaaen. He had income from making dishes (utensil ) from leafs of dates trees and selling them. He had a poor life and used his small room in Madaaen as a shop, governmental office and home. So in Islam, can a scholar receive salary for Islam or should he have his own business to make a living and keep his independence from any government or King? What do Quran and Hadith say about this?