Suhoor (pre-dawn meal) which is called Sahur, Sahari, Sehri, and pisht lamae, is a Sunnah. It is having something (at least water) after half of the night before Fajr.

However, it is not mandatory to have Suhoor.

Thus, in the worship of fasting, there are manners and sunnah that are encouraged and one of it is eating suhoor. The Prophet PBUH encourages his ummah to take their suhoor for there are numerous advantages and blessings in it.

This is in accordance with a hadith narrated by Anas bin Malik RA, where the Prophet PBUH said:

تَسَحَّرُوا فَإِنَّ فِي السَّحُورِ بَرَكَةً (Take Suhur as there is a blessing in it)

Sahih al-Bukhari (1923)