I want to know whether Hazrat Isa , peace be upon him, was a Muslim as some people say that he was not a Muslim. And what about the other prophets?
One who believes in heavenly guidance, teachings and having the doctrine of the Hereafter, is called a Muslim, and all the Prophets, peace be upon them, including Hazrat Isa (peace be upon him) were the bearers, advocates and guides of these teachings. However, since some instructions were also given to different Prophets (peace be upon them) according to their times and circumstances, their followers were used to be called by many a different names attributed to their Prophets, such as Christians etc. And due to successive prophets who came later, old specific teachings of the predecessors were canceled and the teachings of the incumbent Prophet were used to be followed. Similarly, due to the advent of Prophet Muhammad (Sallallahu Alaihi wa Sallam) as well, the old teachings were abrogated. As such, those who believe in old teachings are not called Muslims anymore, and the Muslims now are, only those who believe in the incumbent Prophet Muhammad (Sallallahu Alaihi wa Sallam). Those who do not believe are called by their previous names and these names are now used as a sign of their disbelief and denial of the existing heavenly books.
قال اللہ تعالیٰ: ﴿ اٰمَنَ الرَّسُوْلُ بِمَآ اُنْزِلَ اِلَيْہِ مِنْ رَّبِّہٖ وَالْمُؤْمِنُوْنَ۰ۭ كُلٌّ اٰمَنَ بِاللہِ وَمَلٰىِٕكَتِہٖ وَكُتُبِہٖ وَرُسُلِہٖ۰ۣ لَا نُفَرِّقُ بَيْنَ اَحَدٍ مِّنْ رُّسُلِہٖ۰ۣ وَقَالُوْا سَمِعْنَا وَاَطَعْنَا۰ۤۡ غُفْرَانَكَ رَبَّنَا وَاِلَيْكَ الْمَصِيْرُ۲۸۵﴾ البقرة: ٢٨٥
و فی البداية والنهاية: عن أبي هريرة قال: قال رسول الله - صلى الله عليه وسلم - : " أنا أولى الناس بعيسى عليه السلام والانبياء أخوة أولاد علات وليس بيني وبين عيسى نبي " و عن عبد الرحمن بن آدم، عن أبي هريرة عن النبي- صلى الله عليه وسلم - قال: " الانبياء أخوة لعلات ودينهم واحد وأمهاتهم شتى(2 / 117) والله أعلم بالصواب!