Note: Include The Muslim Ummah In Your Du'as.

💐 In The Name Of Allah The Most Gracious The Most Merciful
💌 A first wife praying to Allah that He guides her husband's second wife to Islam... 
A married woman praying that Allah blesses the marriage life of her friend, praying that the hearts of her co-wives are softened so they can welcome her into the family without any hatred and jealousy... 
A Muslim persistently praying to Allah that He grants his/her relatives guidance and Taqwa even if they have prevented means of communication...
A Muslim who was offended by so-and-so, who got mistreated and betrayed by several individuals numerous times, yet chooses to forgive them and prays to Allah to pardon their mistakes...
A Muslim praying to Allah Subhaanahu wa Ta'aala that He alleviates the affairs of other Muslims and praying for the Ummah in spite of going through struggles and challenging trials of his own...
Two souls who are mutually attracted to each other yet they sacrifice the attraction and distance themselves from one another fearing Allah, praying that He Subhaanahu wa Ta'aala protects the both of them from zina and fitna...
Two souls who had a fight or misunderstanding yet they simultaneously pray to Allah the Most Forgiving to forgive them and the other person, realizing we're all humans, and Allah loves those believers who are patiently forgiving...
Muslims who pray that their friends' businesses are halal and successful, even though they themselves are temporarily struggling financially...
These are some examples of scenarios where a Muslim wholeheartedly prays to Allah for another Muslim.
When you're kind and strong enough to pray for other Muslims:
1] Your heart becomes more pure and a lot softer than before.
By letting go of egoistic pride and prideful hurt, you gain inner strength that enables you to pass Allah's tests more successfully with rewarding Sabr/patience.
2] The lives of those whom you pray for will Inn-sha-Allah improve significantly, just as you eventually notice improvements in yourself and your journey towards Jannah.
3] Some of Allah's Angels pray for you likewise or whatever good thing you pray for a Muslim you will also be granted at the most befitting time.
📖 Abu Darda RadhiAllahu 'anhu narrated: Allah's noble Messenger Muhammad SallAllahu 'alaihi wa sallam said, "No Muslim servant supplicates for his brother behind his back but that the angel says: 'And for you the same.'"
Source: Sahih Muslim 2732
Grade: Sahih (Authentic) according to Muslim