Al Salamu 'Alaykum.
Imam Nawawi came into conflict with Dhahir Baybars, the ruler of Sham and Egypt. Dhahir requested a fatwa from the scholars that money should be collected in order to prepare an army to fight the Tatars in 658 H. When the Tatars occupied Baghdad and advanced upon Palestine and turned towards Sham, he requested a fatwa while the Tatars were in Palestine that money should be collected to purchase weapons.
Every single scholar issued the fatwa except for an-Nawawi. He said: “I will not provide you with such a fatwa.”
Dhahir asked: “Why not? I want to purchase arms for this struggle, and you refuse to issue a fatwa for it? The entire Ummah and Religion will be exposed to loss.”
He replied: “Because you came to us as a slave who owned nothing, and I see that you now own gardens, servants, slave girls, silver, and gold. So, if you sell all of these things and still need money after that, I will issue the fatwa you seek.”
He said: “Leave Sham.”
And he left and went to a small village in Nawa (his hometown). The scholars came to Dhahir Baybras and said to him: “The scholars of Sham are nothing without Muhi ad-Din an-Nawawi.”
He replied: “Bring him back.” They then went to an-Nawawi and said: “Come back, O Muhi ad-Din.”
Nawawi said: “By Allah, I will not go back while Dhahir is in it,” and Allah fulfilled his oath: Dhahir died a month later, and an-Nawawi returned to Sham.
['Fi Dhilal Surat at-Tawbah'; p. 67-68]
Taken from Iskandrani.