The spiritual strengths arising from mutual love and solidarity among believers

At the basis of relationships between people who do not believe in Allah and the Hereafter generally lie the importance given to worldly values and expectations of worldly benefits. By coming together, these people in one sense establish a mutual interest pact; the parties reciprocally support one another and seek to obtain mutual advantages.  The parties of this alliance know that their solidarity is not based on any trust or friendship and, even though they may never say it out loud, that the alliance is a conditional one. When an element that provides a benefit for one of the parties ceases to exist, the alliance ceases to exist, too. Once these conditions are established, one person is not the lightest bit interested whether or not the other is in need or difficulties. Because the alliance established is a union of forces and based solely on an expectation of gain. It is therefore quite natural for the union to fall apart when the gains are impaired. As Allah reveals in the verse "... 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) no matter how much unbelievers may appear to be unified and enjoy solidarity, they can never essentially be so. The only power on Earth that can make true friendship and alliance between people possible is ‘faith.’ Through their friendships, believers who fear the Day of Judgment lay the foundations of a strong alliance that begins in this world and will continue forever in the Hereafter. They love each other and are friends with one another for Allah’s approval alone, not out of any expectation of gain or advantage. Unless Allah so ordains, it is impossible for this bond based on love and fear of Him to be broken. 

With the strength bestowed on them by loving one another for Allah’s approval, believers constitute a very great spiritual force. As revaled in another verse,"... 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) even a few people with faith in their hearts acquire the enthusiasm and determination to overcome great troubles and difficulties. Because of the moral virtues they display, they gain Allah’s help and support. As Allah reveal in the verse, “... You shall be uppermost if you are believers.” (Surah Al-‘Imran, 139) they represent a force that can never be broken, and nobody can ever turn them against one another.

Because they genuinely seek Allah’s good pleasure among themselves, they never fall out or enter into disputes or conflict. Because Allah’s word is one, and the verses of the Qur’an are unequivocal. Since all believers abide unconditionally by the Qur’an and always act in a way intended to do best to earn good pleasure of Allah, the result is great order and harmony. Everything can be resolved easily in an order. Since everyone favors the moral values of the Qur’an and the interests of believers when there is a conflict with their own interests, the result is powerful solidarity.

Because they intend to be one another’s eternal friends in the Hereafter, believers are bound to each other with a deep love, respect and loyalty. They therefore never permit any room for rivalry, friction or dispute. No matter what troubles or difficulties they may be confronted by, thanks to their fear of and sincere faith in Allah, they never fall into defeatism, compromise, giving-up or weakness of mind. If someone has a flaw, others support that person with proper moral values and encourage them toward good. Since they constantly command one another to do good and avoid evil, they constantly grow in faith and strength. This passage from Bediüzzaman Said Nursi describes this spiritual strength possessed by believers, who share the same endeavors and prayers, that arises from their faith and love: 
 

‘Because in the same way that one hand does does not rival the other, one eye does not criticize the other, the tongue does not object to the ear, the heart sees no flaws in the soul.  They may compensate for one another’s deficiencies, cover up each other’s flaws, help meet each other’s needs and assist one another in their work; otherwise, the life of that person’s body will come to an end, the soul will flee and the body decay. In the same way that the cogs in a factory do not compete against one another, try to excel over one another or identify and criticize one another’s flaws or try to wear one another down. They do all they can to assist one another in their common purpose and move toward the purpose behind their creation in genuine solidarity and union. If the slightest aggression or despotism is allowed in, the factory will be harmed and production will stop. Then the owner of the factory will tear it down and scatter its parts...’  (Risale-i Nur Collection, 21st Ray, pp. 668-669)

Bediüzzaman’s analogy is a very important one in terms of understanding the union and unity stemming from the love between believers.  Because of their genuine love and purity that stems from their faith, they acquire an unshakeable spiritual strength from their mutual love and devotion, in the same way that the machines in a factory constitute a great strength.
 

“Your friend is only Allah and His Messenger and those who believe: those who establish prayer and pay alms, and bow.” (Surat al-Ma‘ida, 55)

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

Words of Our Prophet (saas) Encouraging Love 

Al-Mikdam Ibn Mâ’di Kareb narrates:
"The Messenger of Allah said: "If you love your brother’s moral virtue (for Allah), then tell him."( Al-Kutub al-Sitta (Six Books), Vol. 10, p. 135; Abû Dâwud, Kitab al-Adab 122, (5124); Tirmidhi Zuhd 54, (2393) )

"Give each other gifts and love one another. Give each other food. This will heighten the sustenance provided by Allah.” (Al-Kutub al-Sitta (Six Books), Vol. 16, p. 239)

"The best beloved in the sight of Allah are those who build friendships and who build friendships with him. Those who are least loved in His sight are those who fall out with their friends." ( Ihya'u Ulum al-Din, Imam Ghazali, Vol. 2, p. 365)

"Two brothers (two friends) are like two hands. One washes the other." (Ihya'u Ulum al-Din, Imam Ghazali, Vol. 2, p. 394)

"Do not turn your backs on one another. Do not hate one another. Do not envy one another. Do not put an end to your friendships. Be brothers and servants of Allah.”  (Muslim, Ihya'u Ulum al-Din, Imam Ghazali, Vol. 2, p. 407)

"Love Allah for the blessings He gives you, and love me because Allah loves me.”  (Tirmidhi, Ihya'u Ulum al-Din, Imam Ghazali, Vol. 4, p. 594)

"Allah raises those who are humble for His sake. Allah humbles the proud. Allah loves those who remember Him often.”  (Ibn Majah, Ihya'u Ulum al-Din, Imam Ghazali, Vol. 4, p. 655)