The Quran

وَلَقَد أَرسَلنا رُسُلًا مِن قَبلِكَ مِنهُم مَن قَصَصنا عَلَيكَ وَمِنهُم مَن لَم نَقصُص عَلَيكَ ۗ وَما كانَ لِرَسولٍ أَن يَأتِيَ بِآيَةٍ إِلّا بِإِذنِ اللَّهِ ۚ فَإِذا جاءَ أَمرُ اللَّهِ قُضِيَ بِالحَقِّ وَخَسِرَ هُنالِكَ المُبطِلونَ

Muhammad Asad

And, indeed, [O Muhammad,] We sent forth apostles before thy time; some of them We have mentioned to thee,¹ and some of them We have not mentioned to thee. And it was not given to any apostle to bring forth a miracle other than by God's leave.² Yet when God's will becomes rqanifest,³ judgment will [already] have been passed in all justice, and lost will be, then and there, all who tried to reduce to pothing [whatever they could not understand].⁴

I.e., in the Qur'an.
See 6:109 - "Miracles are in the power of God alone" - and the corresponding note 94. Both passages (6:109 and the present one) relate to the futile demand of Muhammad's opponents to be shown a miracle in proof of the divine origin of the Qur'an - the implication being that it is not God's will to convince the deniers of the truth by means of what is commonly regarded as "miracles".
Lit., "when God's command comes", i.e., whether it be in this world or on the Day of Judgment: a reference to the retribution spoken of in verse 77 above.
I.e., in this case, divine revelation as such. For the above rendering of al-mubtilun, see note 47 on the last sentence of 29:48.