Fard Ain
This refers to the religious order that is obligatory for every Muslim individually. If a person does not fulfill it themselves, they are sinful, even if other people are fulfilling it.
That is, Fard Ain are those acts of worship or commands for the fulfillment of which every individual is separately responsible.
According to the clarifications of the esteemed jurists, there are fundamentally three situations in which Jihad becomes Fard Ain.
(1)
When the disbelievers occupy any area of the Muslims or send an army to occupy it, and kill or imprison the Muslims of an area, or any similar situation arises.
(2)
The Muslim Amir announces a "Shari'i general mobilization," meaning he tells all Muslims to come out. In this case, except for those Muslims whom the Imam himself stops, it becomes obligatory for all other Muslims to come out, regardless of their condition.
(3)
When the enemy is confronted, and the battle horn is sounded, then Jihad, which was previously Fard Kifaya, becomes Fard Ain for every person present in the army, and it becomes forbidden to flee.
Please see the references
(Al-Jami' li-Ahkam al-Qur'an lil-Qurtubi/ p. 138/ vol. 8 under the saying of Allah Almighty "Infiru Khifafan wa Thiqalan")
( Al-Fiqh al-Islami wa Adillatuhu al-Zuhayli/ p. 585 / vol. 8/ Al-Bab al-Rabi'/ Al-Fasl al-Awwal/ Rashidiyah Quetta)
(Al-Mabsut li-Kasar Khassi/ p. 4/ vol. 10/ T Rashidiyah Quetta )
Radd al-Mukhtar/ vol. 4/ p. 198/ Kitab al-Jihad/ Matlab fi al-Furu' bayna Fard al-Ain wa Farq al-Kifayah, T.) (Rashidiyah Quetta
(Al-Mughni li-Ibn Qudamah Hanbali/ vol. 10/ p. 341/ al-Raqam)
(Al-Musalsal 7413/ Kitab al-Jihad/ T. Dar al-Fikr Beirut
To be continued,,,,,,,"""