Why was there any need for qir'aat and can you please provide a hadith or a verse from the quran?

Question
Why was there any need for qir'aat and can you please provide a hadith or a verse from the quran
 jazaka allahu kheir

Answer
It is well established that the Qur'an was revealed in seven "ahruf" or ways of recitation.  These "ahruf" incorporate the different dialects of the Arabs and in them is an ease for the Arabs of different areas to recite the Qur'an.   Some areas of Muslims read with imaalah, others read by changing the hamzah if it is saakinah or if two hamzahs occur right after each other, etc.  So the different qir'aat made it easy for the Arabs of each area to learn the Qur'an.
The following ahaadeeth demonstrate this:
Ubayy b. Ka'b reported that the Prophet of Allaah (sallAllaahu alayhi wa sallam) was near the tank of Banu Ghifar that Gabriel came to him and said: Allaah has commanded you to recite to your people the Qur'an in one "harf" [or dialect or way]. Upon this he said: I ask from Allaah pardon and forgiveness. My people are not capable of doing it. He then came for the second time and said: Allaah has commanded you that you should recite the Qur'an to your people in two dialects. Upon this he (the Prophet) again said: I seek pardon and forgiveness from Allaah, my people would not be able to do so. He (Gabriel) came for the third time and said: Allaah has commanded you to recite the Qur'an to your people in three dialects. Upon this he said: I ask pardon and forgiveness from Allaah. My people would not be able to do it. He then came to him for the fourth time and said: Allaah has commanded you to recite the Qur'an to your people in seven ahruf, and in whichever dialect [or harf] they would recite, they would be right.
Muslim 1789

Ubayy b. Ka'b reported: I was in the mosque when a man entered and prayed and recited (the Qur'in) in a style to which I objected. Then another man entered (the mosque) and recited in a style different from that of his companion. When we had finished the prayer, we all went to Allaah's Messenger (sallAllaahu alayhi wa sallam) and said to him: This man recited in a style to which I objected, and the other entered and recited in a style different from that of his companion. The Messenger of Allaah (sallAllaahu alayhi wa sallam) asked them to recite and so they recited, and the Prophet of Allaah (sallAllaahu alayhi wa sallam) expressed approval of their affairs (their modes of recitation). and there occurred In my mind a sort of denial which did not occur even during the Days of Ignorance. When the Messenger of Allaah (sallAllaahu alayhi wa sallam) saw how I was affected (by a wrong idea), he struck my chest, whereupon I broke into sweating and felt as though I were looking at Allaah with fear. He (the Prophet) said to me: Ubayy. a message was sent to me to recite the Qur'an in one dialect, and I replied: Make (things) easy for my people. It was conveyed to me for the second time that it should be recited in two dialects. I again replied to him: Make affairs easy for my people. It was again conveyed to me for the third time to recite in seven dialects And (I was further told): You have got a seeking for every reply that I sent you, which you should seek from Me. I said: O Allaah! forgive my people, forgive my people, and I have deferred the third one for the day on which the entire creation will turn to me, including even Ibrahim (sallAllaahu alayhi wa sallam) (for intercession). 
Muslim 1787

Ibn 'Abbas reported Allaah's Messenger (sallAllaahu alayhi wa sallam) as saying: Gabriel taught me to recite in one style. I replied to him and kept asking him to give more (styles), till he reached seven modes (of recitation). Ibn Shibab said: It has reached me that these seven styles are essentially one, not differing about what is permitted and what is forbidden.
Muslim 1785