Is Saying Insha Allah Fard?
Yes, it’s a commandment of Allah, so it’s obligatory. Please see verses 18:23-24 of Holy Quran: 18:23 You shall not say that you will do anything in the future 18:24 without saying, “GOD willing.” If you forget to do this, you must immediately remember your Lord and say, “May my Lord guide me to do better next time.”, This important commandment also gives us daily opportunities to remember Allah. Mighty not be obligatory to state in Arabic, you can also say in your own tongue.