The strength of believers is derived from their sincerity

In general, the association of those who do not believe in Allah and the hereafter is based on the importance they attach to worldly goods and the hope for worldly rewards. By their association, such people may conclude an agreement out of mutual interests. Each party supports the other, and thus, they hope to obtain mutual benefit. Without admitting it, those who form such alliances know that their association is not based upon mutual trust or friendship, and that their participation is conditional. When one of the parties is no longer of benefit to the other, then the alliance is terminated. The opposing party remains indifferent to the needs of the party in difficulty. Hence, such alliances only arise merely from the hope of greater strength through increased numbers and for the attainment of some worldly gain. Therefore, it is to be expected that such an alliance would disintegrate as soon as the possibility of attainting these things vanishes. As Allah informs mankind in the Qur'an, the hearts of those who deny Allah are not inclined to one another, even if they appear externally to be as one single body:

... Their hostility towards each other is intense.They are full of bravado in each other's company. You consider them united but their hearts are scattered wide. That is because they are people who do not use their intellect. (Surat al-Hashr: 14)

For this reason, such alliances formed among those who deny Allah are always prone to fall apart. In this world, there is only one thing capable of ensuring a true unity, real friendship and alliance among men, and that is "faith." When those of true faith, who fear the Day of Judgment, unite in this world, they lay the foundations of a sound alliance, which will last eternally into the hereafter. They love and befriend each other solely for Allah's sake. They unite with sincere intentions, without expecting any other benefit. This union takes its origin from love and fear of Allah, the only true source of alliance. Therefore, it is impossible for it to be destroyed unless Allah wills so. Believers form a power resembling "a well-built wall" that cannot be penetrated. The verse quoted below declares as follows:

Allah loves those who struggle in His Way in ranks like well-built walls. (Surat as-Saff: 4)

Those who have faith and who are sincere are granted the determination and enthusiasm to overcome, even if they are outnumbered by millions. This is stated in the following verse as follows:

... But those who were sure that they were going to meet Allah said, "How many a small force has triumphed over a much greater one by Allah's permission! Allah is with the steadfast." (Surat al-Baqara: 249)

They gain Allah's support by always remaining sincere. Since Allah is the "Unconquerable (Al-Aziz)," they ultimately succeed. They are aware of the secret announced in the verses of Allah as, "…You will be uppermost if you are [true] believers." (Surah Al 'Imran: 139). Consequently, they are extraordinarily resiliant and powerful, a quality to which the discord, disagreement and suspicion created by the outsiders cannot penetrate.

Each of those who form such a union fears Allah, and surrenders himself unconditionally to the verses of the Qur'an. As they strive solely to gain Allah's consent, and fear none but Allah, each is like an entire army.