In a very famous Ayat the Holy Quran states that there is no compulsion in Islam .At other place it clearly states that for you your religion and for me my religion. The Prophet (pbuh) signed an agreement with all religious groups of Madina , the Jews, non believers and tribes giving full freedom to practice their religion and practices. Thus in my view it was an agreement which can only be termed as SECULAR.
Moreover if some religion and community which badly needs SECULARISM it is Muslims and Islam . Muslims are killing their coreligionists in hundreds of thousands, these days in the name of divergent Sharias and contradictory interpretations of Islam. Right after the death of the Prophet Muslims have killing Muslims due to contradictory interpretations. TTHUS MUSLIMS NEED SECULARISM MORE THAN ANYONE ELSE TO SURVIVE AS HUMANS.