Roza Rakhne / Sehri Ki Dua (Niyyah)
At Suhoor/Sehri, intention to fast
وَبِصَوْمِ غَدٍ نَوَيْتُ مِنْ شَهْرِ رَمَضَانَ
Wa bi sawmi ghadin nawaytu min shahri Ramadan.
Tarjuma Aur main Ramadan ke mahine ke kal ke roze ki niyyat karta/karti hoon.
And I intend to keep tomorrow's fast of the month of Ramadan.
Reference This exact Arabic phrase is a popular subcontinental niyyah formula, not a hadith. The obligation of intention itself comes from the hadith "Actions are but by intentions" (Sahih al-Bukhari 1, Sahih Muslim 1907).
Kab Aur Kyun Padhein
Yeh roza rakhne ki dua sehri ke baad, Fajr se thodi der pehle padhi jaati hai. Most people in India learn this line during sehri, and reciting it is a good, simple way to fix your niyyah before Fajr.
The heart of roza is the intention, and this phrase just helps you put that intention into words.
Zaroori Baat
Be clear on one thing: niyyah is fundamentally an act of the heart, not a fixed Arabic sentence. This exact wording is a widely-used aid, not an obligatory formula from the Prophet ﷺ. If you simply know in your heart that you are fasting tomorrow for Allah, your niyyah is valid. In the Hanafi view (which most Indian Muslims follow) the intention for a Ramadan fast can even be made up until roughly midday if you forgot at sehri, though making it at night is better and safer.