What is the obligatory measure of supplication for oppressed Muslims? Has supplicating for them at all times and sponsoring their orphans become obligatory after it was [merely] recommended? And is it literally necessary to supplicate at all times with presence of heart?

Supplicating for an oppressed Muslim is commendable and carries great reward, as it is authentically reported that the Prophet, peace and blessings be upon him, used to supplicate for the oppressed among the believers. The general principle is that supplicating for Muslims is commendable, and some scholars have considered it a charity without money, and it may even be better than giving monetary charity. Imam al-Nawawi mentioned that supplicating for Muslims for their well-being and for warding off harm from them is the view of all scholars. And the presence of the heart is among the reasons for the supplication to be answered.