Can a person say to his friend “Ya Khaleeli (O my close friend)”?
Question

If a person says to his friend, “You are my khaleel (close friend),” or says “So and so is my khaleel”, what is the ruling on that? I hope that you can explain to me because I am confused and do not know how I should respond if someone says that to me.
Praise be to Allah.There is nothing wrong with a person saying to one whom he loves for the sake of Allaah, “You are my khaleel (close friend)”. Some of the Sahaabah used this word with regard to the Prophet (peace and blessings of Allaah be upon him). Khillah (close friendship) is the highest form of mahabbah (love). 
But the Prophet (peace and blessings of Allaah be upon him) had no khaleel (close friend) because Allaah took him as a close friend. But this does not contradict what the Sahaabah said about regarding him as their khaleel, because it is not a condition of khillah (close friendship) that each party regards the other as a khaleel. 
It was narrated that Abu Dharr said: I heard the Prophet (peace and blessings of Allaah be upon him) say, five days before he died, “I declare before Allaah that I have no khaleel from among you, for Allaah has taken me as a khaleel as He took Ibraaheem as a khaleel. But if I were to have taken anyone from among my ummah as a khaleel, I would have taken Abu Bakr as a khaleel. But those who came before you used to take the graves of their Prophets and righteous men as places of worship. Do not take graves as places of worship, for I forbid you to do that.” 
Narrated by Muslim, 532. 
And it was narrated that Abu Hurayrah (may Allaah be pleased with him) said: My close friend (khaleel – i.e. the Prophet (peace and blessings of Allaah be upon him)) enjoined three things upon me that I will not give up until I die: fasting three days of each month, praying Duha, and sleeping after Witr. 
Narrated by al-Bukhaari, 1124; Muslim, 721. 
Al-Haafiz Ibn Jahar said: 
The khaleel is a sincere friend whom one takes as a close friend because love for him takes deep root in one’s heart.  There was some scholarly dispute as to whether khillah (close friendship) is of a higher status than mahabbah (love) or vice versa. These words of Abu Hurayrah do not contradict what we have quoted above from the Prophet (peace and blessings of Allaah be upon him): “But if I were to have taken anyone from among my ummah as a khaleel, I would have taken Abu Bakr as a khaleel”, because the fact that he (peace and blessings of Allaah be upon him) did not take anyone as a close friend does not rule out the opposite, and no one says that close friendship can only be complete if each party regards the other as a khaleel, because the Sahaabi looked at this relationship from his own point of view, or perhaps he only meant companionship and love.  
Fath al-Baari, 3/57 
This word was narrated from Abu Hurayrah (may Allaah be pleased with him) more than once. 
This word was also used by the great Sahaabi Abu Dharr al-Ghifaari with regard to the Prophet (peace and blessings of Allaah be upon him), as was narrated by al-Bukhaari, 1342; Muslim, 992. And it was mentioned in another hadeeth narrated by Muslim, 648. 
It is worth pointing out here that we should think before we speak such words that indicate deep love and sincere friendship, and look at the basis and purpose of the relationship, and ensure that it is far removed from any haraam attachment or things that are not pleasing to Allaah, so that it will not be a source of loss and regret on the Day of Resurrection: 
“Friends on that Day will be foes one to another except Al-Muttaqoon (the pious)”
[al-Zukhruf 43:67]
And Allaah knows best.