[This section is taken from the words of Shaykh Sâlih Uthaymeen – may Allâh bestow mercy on him – in Fat'hul-Dhil-Jalaal Wal-Ikraam Shar'h Buluugh Al-Maraam
You should know that every obligatory act has a condition (among others): The ability to carry it out. The proof for that are various texts in the Book of Allâh and the Sunnah of His Messenger – SallaLlâhu alahy wa sallam –; another proof is what happens around us (Al-Waaqi).
As for what has come in the Qur'ân, Allâh the Majestic said:
Allâh burdens not a person beyond his scope. [Al-Baqarah: 286].
Allâh the Majestic also said:
So keep your duty to Allâh and fear Him as much as you can [Taghaabun: 16].
He the Mighty also said:
Strive hard in Allâh's Cause as you ought to strive. He has chosen you (to convey His Message of Islâmic monotheism to mankind by inviting them to his religion, Islâm), and has not laid upon you in Religion any hardship [Hajj: 78].
The meaning of the (last) Verse is that 'if you are commanded of Jihâd and there is no incapacity in carrying it out, no problem; but if there is, the obligation is removed.' Therefore, there is no way the conditions of capacity and ability must not be met (in carrying out Jihâd).
From the Sunnah; the Prophet – SallaLlâhu alahy wa sallam – said:
'When I command you of a matter, carry it out as you can…' [Recorded by Muslim (1337)].
The statement of the Prophet – SallaLlâhu alahy wa sallam – above applies to all matters (of the Deen) whether matters of worship or Jihâd.
Another proof for capacity and ability in carrying out Jihâd (as an obligation) is what happened in the life of the Messenger of Allâh – SallaLlâhu alahy wa sallam –. When he – SallaLlâhu alahy wa sallam – was in Makkah, he was calling people to and to Prayer. He was upon this for about thirteen years; he was not commanded to carry out the Jihâd despite the great harm he and his followers were encountering from the unbelievers, and despite the less burden. The bulk of the pillars of the Deen became obligatory when he – SallaLlâhu alahy wa sallam – arrived in Madeenah. Were they (however) commanded to fight (in Makkah)? No! Why? Because they were not capable; they were fearing for themselves. It is well known that the Prophet – SallaLlâhu alahy wa sallam – left Makkah fearing for himself; that was why Allâh the Majestic did not command that there should be fighting except after the Ummah of Islam had become a powerful state. [After that it was revealed:]
Permission to fight is given to those (i.e. believers against disbelievers), who are fighting them, (and) because they (believers) have been wronged, and surely, Allâh is Able to give them (believers) victory [Hajj: 39].
[Then Shaykh Uthaymeen – may Allâh bestow mercy on him – said:]
If someone were to ask; why don't we fight the US, Russia, France and the UK now?
The answer to that is to say we would not fight them because we do not have the ability. We have outdated weapons which if compared with theirs, are like knifes with missiles; the former will be of no use. How can we then fight them?
Therefore I say, it is of utmost stupidity that someone should say that we should fight the US, France, the UK and Russia now. This not justifiable under the Wisdom of Allâh the Majestic and neither under His Shariah. But what is imperative upon us is to carry out what Allâh has commanded us to do:
And make ready against them All You can of power [Al-Anfaal: 60].
This is what is imperative, that we should prepare for them what we can of power; and the best of power is Faith (in Allâh) and fear (of Him); with both, we shall be able to overpower our desires, weakness, love for the world; indeed we love the world and we detest death… and among what is important that we should prepare for our enemy is that we should not be divided while we are under a single banner or many banners. How many countries make up the Islamic Nation today? Many countries! While in the advent of Islam it was just a single nation. The countries have become plenty today. Are the (Muslim) countries united or divided? They are indeed very divided to the highest degree. And even in the case of one country, are its people united? The best answer to that is the negative. Most Islamic countries are filled with parties – political and religious, moral and methodological. Go out of your country and see the profound amazement; each village (posing as a country) sees itself as an independent country on its own belief, methodology, acts and judicial system; how then can we become victorious over our enemy?
[End of quoting from, Fat'hul Dhil-Jalaal Wal Ikraam Bi Shar'h Buluughil-Maraam, pp. 437-439].