The Quran

وَلا تُؤمِنوا إِلّا لِمَن تَبِعَ دينَكُم قُل إِنَّ الهُدىٰ هُدَى اللَّهِ أَن يُؤتىٰ أَحَدٌ مِثلَ ما أوتيتُم أَو يُحاجّوكُم عِندَ رَبِّكُم ۗ قُل إِنَّ الفَضلَ بِيَدِ اللَّهِ يُؤتيهِ مَن يَشاءُ ۗ وَاللَّهُ واسِعٌ عَليمٌ

Muhammad Asad

but do not [really] believe anyone who does not follow your own faith." Say: "Behold, all [true] guidance is God's guidance, consisting in one's being granted [revelation] such as you have been granted."¹ Or would they contend against you before your Sustainer? Say: "Behold, all bounty is in the hand of God; He grants it unto whom He wills:² for God is infinite, all-knowing,

This refers to the Jews and the Christians, who are not prepared to accept the Qur'anic message on the ground that it conflicts with parts of their own scriptures.
In this context, the term fadl ("bounty") is synonymous with the bestowal of divine revelation.