Qur'an Surah 112 - 'Say; He is Allah, the one and only...' - it shows Tawhid.
At the beginning of each Surah (except the 9th) - 'In the name of Allah, the entirely merciful, the especially merciful...' - shows Allah's mercy
From Qur'an - 'From Allah, verily nothing is hidden on earth or in heavens' - shows that Allah knows all our intentions (Niyyah) and he is omniscient and will, therefore, judge us fairly
From Sahih al-Bukhari - One will come back from Hajj 'as if he were born anew' - shows the importance of Hajj
From Qur'an 'The heart did not lie [about] what it saw' - shows that the Qur'an is the incorrupt word of God.
Shahadah - 'there is no God but Allah and Muhammad is his prophet'
Qur'an - 'Prayer prohibits immorality and wrongdoing' - shows Salah is important
Honestly, DO NOT stress you will be fine. If you can't think of any quotes just say something like 'In the Qur'an... Allah is portrayed as loving as he made the universe for us' or something like that. You don't need to know really specific references for GCSE. Good luck - I'm hoping they will give us nice 12 markers !!!