[2:191] And slay them wherever you come upon them,
It means 'it is incumbent on you to show enmity towards My enemies, just as it is incumbent on you to establish friendship (walāya) and assistance (muwālāh) with My friends (awliyāÌ). So do not spare them, even if there are bonds of kinship or close relation between you'.
[2:191 cont'd] and expel them from where they expelled you;
'Firstly, expel [your] love for them and their friendship from your hearts, then drive them from the regions of Islam so that they will be diminished'.
[2:191 cont'd] sedition is more grievous than slaying.
The allusion is that the ordeal that comes to hearts (qulūb) from the misfortunes of veiling is more grievous than that which comes to the bodily selves (nufūs) from the exertion of the spirit (rūḥ), because the passing away of the life of the heart is more grievous than the passing away of the life of the bodily self. This is because the life of bodily selves is through what is fitting and familiar to them, but the life of the heart can only be through God.
It is said sedition is more grievous than slaying means that remaining apart from God is much worse than remaining with your spirit (ruḥ) and your life.
[2:191 cont'd] But fight them not by the Sacred Mosque until they should fight you there; then if they fight you, slay them - such, is the requital of disbelievers.
The allusion in it: 'Do not disturb your moment (waqt) with God, letting in the attributes that characterize the bodily and lower self, even if that be supererogatory acts of obedience. If a noisy preoccupation distracts you from God, remove that matter from your self by every means possible so that no attachment will remain for you that blocks you from God'.