Dua for Fasting (Niyyah)
بِسْمِ اللَّهِ
وَبِصَوْمِ غَدٍ نَّوَيْتُ مِنْ شَهْرِ رَمَضَانَ
Bismillah
In the name of Allah
Wa bisawmi ghadinn nawaiytu min shahri Ramadan
I intend to keep the fast for tomorrow in the month of Ramadan
NOTE: There is no reference in Hadith for this Dua.