The Quran

وَيَستَعجِلونَكَ بِالسَّيِّئَةِ قَبلَ الحَسَنَةِ وَقَد خَلَت مِن قَبلِهِمُ المَثُلاتُ ۗ وَإِنَّ رَبَّكَ لَذو مَغفِرَةٍ لِلنّاسِ عَلىٰ ظُلمِهِم ۖ وَإِنَّ رَبَّكَ لَشَديدُ العِقابِ

Muhammad Asad

And [since, O Prophet, they are bent on denying the truth,] they challenge thee to hasten the coming upon them of evil instead of [hoping for] good¹although [they ought to know that] the exemplary punishments [which they now deride] have indeed come to pass before their time. Now, behold, thy Sustainer is full of forgiveness unto men despite all their evildoing:² but, behold, thy Sustainer is [also] truly severe in retribution!

Lit., "they ask thee to hasten the evil before the good": i.e., instead of willingly accepting the guidance offered them by the Prophet, they mockingly challenge him to bring about the exemplary punishment with which, according to him, God threatens them. (For a fuller explanation of this "challenge", referred to here and in several other places in the Qur'an, see 6:57-58 and 8:32, as well as the corresponding notes.)
Cf. the first sentence of 10: 11 and the corresponding note 17.