The philosophy behind Jihad and war against the infidels
وَلَوْلَا دَفْعُ اللَّـهِ النَّاسَ (And had Allah not repelled some people by means of some others... - 22:40) Had Allah not repelled some people by means of some others, the monasteries, the churches, the synagogues and the mosques where the name of Allah is recited abundantly would have been demolished. The command to take up arms against the unbelievers is nothing new, because the earlier prophets and their followers had received similar orders from Allah Ta’ ala and the philosophy behind this command was that without armed resistance no religion would have felt safe and their places of worship would have been destroyed by the infidels.
There have been many religions which were founded on the worship of one God and built up by means of Wahy (Divine revelations). In course of time their basics were changed and so many alterations were introduced in them that they turned into unbelief and polytheism. But before these things happened, they were true religions and it was the duty of their followers to respect and defend their places of worship. This verse refers to such places of worship only and does not include the sacred places of those religions which were not founded on prophethood and revelation (such as the fire-worshiping Magians, or the idol-worshiping Hindus) because they were at no time considered places deserving of respect.
In this verse صَوَامِعُ is the plural of صَوَمِعُہ ، which means a monastery which is a place of worship meant for Christian monks and hermits بِيَعٌ is the plural of بِیعَۃ ، which means a Christian church, and صَلَوَاتٌ is the plural of صلُوت ، which means a Jewish synagogue. And of course مَسَاجِدُ is the place of worship of the Muslims.
The meaning of this verse is that if at different times the believers had not been permitted to fight the infidels, no true religion would have felt secure and at different times during the periods of Sayyidna Musa (علیہ السلام) ، Sayyidna ` Isa (علیہ السلام) and the Holy Prophet ﷺ the places of worship of their respective religions would have been destroyed. (Qurtubi)