According to a hadith, Copy Arabic text

This means, "God says, 'My love is assured for those two who love each other for My sake.'" If two people love each other for God's sake, then God's love is guaranteed to them. This tells us the sacrifice we need to make in this world. If you engage in religious work, such as dawah, then such kind of work cannot be done all alone. You can perform this work only in cooperation with others. If you engage in dawah work along with others, repeatedly you will have complaints with others. Complaints are a part of nature. There will never be a situation in which complaints are eliminated. 
The Companions of the Prophets had complaints. Even when two prophets were sent together, they developed complaints about each other. This has been mentioned in the Quran. Both Moses and Aaron were prophets. 
They developed complaints on a matter. On one occasion, Aaron said to Moses: "Son of my mother! Do not seize me by my beard nor by my head." (20:94)

Complaints are a part of nature.
One has to rise above complaints and preserve feelings of love for others. This is so that the team remains united and all can work together with one another. To work together with others it is essential to rise above the mentality of complaints. One will inevitably have complaints. It is impossible for two, four or ten people, who are working together, to not have complaints about one another. 
This is why God has said that His love is guaranteed to those who love one another in spite of complaints, for the sake of religion and for the sake of God. In our dawah work, there will be repeated experiences of being united for dawah, but also becoming divided due to complaints. People will come together to convey the message of God. But when we work together, we will definitely have complaints. And some will distance themselves from others due to these complaints. 
Such people do not deserve the love of God. God will not take pride on such people.
People on whom God takes pride are those who rise above complaints and live only for the sake of God. They are those who maintain good relations with others and love them only for God's sake. Such people always keep complaints aside. They avoid complaints. They forget complaints.