You do not engage in any matter or recite any of the Qur'an or do any action without Our witnessing you while you are occupied with it. Not even the smallest speck eludes your Lord, either on earth or in heaven. Nor is there anything smaller than that, or larger, which is not in a Clear Book. (Qur'an, 10:61)
Say: 'Allah is a sufficient witness between me and you. He is certainly aware of and sees His servants.' (Qur'an, 17:96)
Those who do not believe say, 'You are not a Messenger.' Say: 'Allah is a sufficient witness between you and me, and anyone else who has knowledge of the Book.' (Qur'an, 13:43)
We will show them Our Signs on the horizon and within themselves until it is clear to them that it is the truth. Is it not enough for your Lord that He is a witness of everything? (Qur'an, 41:53)