There is a lot of textual evidence from the Book and the Sunnah supporting these fundamentals as well as a consensus amongst the Ummah concerning them.
Allah the Glorified said:
It is not Al-Birr (piety, righteousness, and every act of obedience to Allah) that you turn your faces towards the east and (or) the west (in prayers); but Al-Birr is (the quality of) the one who believes in Allah, the Last Day, the Angels, the Book and the Prophets…Al Baqarah: 177
He also said:
Indeed, We have created all things with Qadar (Divine Decree) Al Qamar: 49
The Messenger (Muhammad - صلى الله عليه وسلم -) believes in what has been sent down to him from his Lord, and (so do) the believers. Each one believes in Allah, His Angels, His Books, and His Messengers. (They say,) "We make no distinction between His Messengers"Al Baqarah: 285
…and whosoever disbelieves in Allah, His Angels, His Books, His Messengers, and the Last Day, then indeed he has strayed far away.An Nisaa: 136
In an authentic Hadeeth the Prophet - صلى الله عليه وسلم -said:
Eemaan [faith] is to believe in Allah, His angels, His Books, His Messengers, and to believe in al Qadr [Devine Decree] whether good or bad.
All the Messengers, every legislation and all revealed Books came with these tremendous fundamentals, and they are called ‘The Pillars of Faith’, and no one rejects them or a part of them except that he exists the circle of faith and is one of the disbelievers as a result of that, as Allah said:
Verily, those who disbelieve in Allah and His Messengers and wish to make distinction between Allah and His Messengers (by believing in Allah and disbelieving in His Messengers) saying, "We believe in some but reject others," and wish to adopt a way in between.
They are in truth disbelievers. And We have prepared for the disbelievers a humiliating torment.
And those who believe in Allah and His Messengers and make no distinction between any of them, We shall give them their rewards; and Allah is Ever Oft-Forgiving, Most Merciful.An Nisaa: 150-152
These tremendous fundamentals, these solid pillars need to be explained and clarified, and we will inshaa-Allah attempt to present what we are able to of it in this book [and this site].