Surah 4. An-Nisaa', Ayah 136

What is meant here is belief in the fact of earlier revelation, and not in the earlier-revealed scriptures in their present form, which - as repeatedly stated in the Qur'an - is the outcome of far-reaching corruption of the original texts.

Since it is through the beings or forces described as angels that God conveys His revelations to the prophets, belief in angels is correlated with belief in revelation as such.

If your belief is by habit or birth or the example of those you love or respect or admire, make that belief more specific and personal to yourself. We must not only have faith, but realise that faith in our inmost being. The chief objects of our Faith are Allah, His Messenger, and His Revelations. To all these we must give a home in our hearts. The angels we do not see and realise as we realise Allah, who is nearer to us than the vehicle of our life-blood, and the Day of Judgment is for our future experience, but we must not deny them, or we cut off a part of our religious view.