Praise be to Allah.
I was very happy to hear that you and your sisters are studying Islamic issues and trying to find out about Islamic views of love. No doubt you and your sisters understand the importance of the scholars views and referring to them in matters of dispute. I will quote here a number of views about love, so that you will understand the matter better, in sha Allaah
Love may be divided into mahabbah khaassah (specific love) and mahabbah mushtarakah (general love).
Mahabbah khaassah (specific love):
Specific love may be divided into types that are halaal and types that are haraam.
Halaal love includes:
(1) Love of Allaah, which is the most important obligation, as it is the basis of Islam. By perfecting ones love of Allaah, one perfects ones faith. If ones love of Allaah is lacking, then ones Tawheed is also lacking. The daleel (evidence) for this is the aayaat (interpretation of the meaning):
. . . But those who believe, love Allaah more (than anything else) . . . [al-Baqarah 2:165]
Say: If your fathers, your sons, your brothers, your wives, your kindred, the wealth that you have gained, the commerce in which you fear a decline, and the dwellings in which you delight . . . are dearer to you than Allaah and His Messenger, and striving hard and fighting in His cause, then wait until Allaah brings about His Decision (torment). And Allaah guides not the people who are faasiqoon (rebellious, disobedient). [al-Tawbah 9:24]
There are also other similar proofs in the Quraan and Sunnah.
Love of Allaah may also take the form of preferring what Allaah loves and wants of His slave to what the slave himself might love and want. So he loves what Allaah loves, hates what He hates, takes as friends or regards as enemies for His sake, and adheres to His laws. There is much that may strengthen this love.
(2) Love of Allaahs Messenger, which is also one of the most important duties of Islaam. Indeed, faith is not complete until a person loves the Messenger of Allaah more than he loves himself, as in the ahaadeeth:
The Messenger of Allaah (peace be upon him) said: None of you truly believes until I am more beloved to him than his child, his father and all the people. (Reported by Muslim, no. 44).
Abdullaah ibn Hishaam said: We were with the Prophet (peace be upon him), and he was holding the hand of Umar ibn al-Khattaab. Umar said to him: O Messenger of Allaah, you are dearer to me than everything except my own self. The Prophet (peace be upon him) said: No (that is not right), by the One in Whose hand is my soul, until I am dearer to you than your own self. Umar said to him, Now, by Allaah, you are dearer to me than my own self. The Prophet (peace be upon him) said: Now (you are right), O Umar. (Reported by al-Bukhaari, no. 6632).
This love is part of loving Allaah and is manifested by following the Prophet (peace be upon him) and preferring his opinion over that of others.
(3) Love of the Prophets and the believers. This is obligatory because loving Allaah dictates that one should love the people who obey Him, in other words the Prophets and righteous people. The daleel (evidence) for this is the hadeeth Whoever loves for the sake of Allaah (i.e., loves the people of faith for the sake of Allaah). Obedience to Allaah is based on love of Allaah. Faith cannot be perfected except in this way, even if one has a lot of prayer and fasting to ones credit. As Umar ibn al-Khattaab said: You have seen us at the time of the Messenger of Allaah: none of us would think that he had more right to his own money than his Muslim brother.
This includes love which constitutes shirk, which is when a person loves something instead of Allaah or as much as Him. In such a case he has taken that thing as a rival to Allaah. This is the shirk of love, and most people have taken things as rivals to Allaah in love and glorification.
There are also types of forbidden love which do not go to the extent of shirk, such as loving ones family, wealth, tribe, business or house, and preferring those things, in whole or in part, over doing the duties that Allaah requires of him, such as hijrah (migration for His sake), jihaad, etc. The daleel (evidence) for this is the aayah quoted above (Say: If your fathers, your sons, your brothers, your wives, your kindred, the wealth that you have gained, the commerce in which you fear a decline, and the dwellings in which you delight . . . are dearer to you than Allaah and His Messenger, and striving hard and fighting in His cause, then wait until Allaah brings about His Decision (torment). [al-Tawbah 9:24])
Mahabbah mushtarakah (general love):
General love is of three types:
(1) Natural love, such as the love of a hungry person for food, or a thirsty person for water. This does not involve any kind of glorification, so it is permissible.
(2) Love based on mercy and pity, such as the love of a father for his small child. This also involves no kind of glorification, so there is nothing wrong with it.
(3) Love based on acquaintance and friendship, such as that between those who share a common profession, or scholars in the same field, or people one meets on a daily basis (such as fellow-commuters), or people one does business with, or travelling-companions. This type of appropriate love between people, or brotherly love, does not imply shirk or associating anyone else in ones love for Allaah.
For more information, see Kitaab Tayseer al-Azeez, Baab wa min al-naas man yattakhidhu min doon-Allaahi andaadan.
We hope that this explanation makes the matter clearer. We ask Allaah to bless you and us with good. May Allaah bless our Prophet Muhammad.