وَبِصَوْمِ غَدٍ نَوَيْتُ مِنْ شَهْرِ رَمَضَانَ
Wa bisawmi ghadin nawaitu min shahri Ramadan
I intend to fast tomorrow in the month of Ramadan.
The intention (niyyah) for fasting should be made before Fajr. It can be a verbal statement or simply the resolve in your heart. The Prophet ﷺ said: "Whoever does not make the intention to fast before Fajr, there is no fast for him."
Related Du'as
تَقَبَّلَ اللَّهُ مِنَّا وَمِنْكُمْ
May Allah accept from us and from you.
Hasanاللَّهُمَّ إِنَّكَ عَفُوٌّ كَرِيمٌ تُحِبُّ الْعَفْوَ فَاعْفُ عَنِّي
O Allah, You are the Pardoner, the Most Generous, and You love to pardon, so pardon me.
Sahihاللَّهُمَّ ارْحَمْنِي بِالْقُرْآنِ وَاجْعَلْهُ لِي إِمَامًا وَنُورًا وَهُدًى وَرَحْمَةً
O Allah, have mercy on me through the Quran, and make it for me a guide, a light, a source of guidance, and a mercy.
Hasanاللَّهُمَّ تَقَبَّلْ مِنَّا إِنَّكَ أَنْتَ السَّمِيعُ الْعَلِيمُ وَتُبْ عَلَيْنَا إِنَّكَ أَنْتَ التَّوَّابُ الرَّحِيمُ
O Allah, accept from us, for You are the All-Hearing, the All-Knowing. And turn to us in mercy, for You are the Acceptor of repentance, the Most Merciful.
Sahih