We have said that love is not restricted only to an animal love of a sexual or parental kind. Rather, there is another kind of love and attraction which is situated in a more rarefied atmosphere, and is completely beyond the confines of matter or materiality. It originates from an instinct far above that of the preservation of generations, and is in fact something which separates the universe of man from the universe of animals. This is spiritual, or human, love, falling in love with excellence and goodness, becoming enamoured of the virtues of man and the beauty of reality.
Those loves which are for the sake of a colour
Are not love: in the end they are a disgrace;
Since love of the dead is not enduring,
Because the dead one never comes back to us.
(But) love of the living is every moment
Fresher than a bud in the spirit and the sight
Choose the love of that Living One Who is everlasting,
Who gives thee to drink of the wine that increases life.
Choose the love of Him from Whose love
All the prophets gained power and glory. 
And it is love which is mentioned in many of the verses of the Qur'an, especially by the word "mahabbah", These verses can be placed in several groups:
1. Verses which describe the believers, and speak of the deep devotion and love they have for God or the other believers,
But those that believe love Allah more ardently. (al Baqarah, 2 :165 )
And those who made their dwelling in the abode, and in belief, before them, love whosoever has emigrated to them not finding in their breasts any need for what they have been given, and preferring others above themselves, even though poverty be their portion. (al-Hashr, 59:9)
2. Verses which speak of the love of God for believers:
Truly Allah loves those who repent, and He loves those who cleanse themselves. (al-Baqarah, 2:222)
And Allah loves the good doers. ( Al `Imran, 3 :148 and al-Ma'idah, 5 :13 )
Surely Allah loves those who guard themselves. (at-Tawbah, 9 : 4 and 7 )
And Allah loves those who cleanse themselves. (at-Tawbah, 9 :108 )
Surely Allah loves the just. (al-Hujurat, 49:9 and al-Mumtahinah, 60:8 )
3. Verses which include two-way affections and reciprocal love: the love of God for the believers, the love of the believers for God; and the love of the believers for each other:
Say "if you love Allah, follow me, and-Allah will love you, and forgive you your sins." (Al `Imran, 3 : 31)
Allah will assuredly bring a people He loves, and who love Him. (al-Ma' idah, 5: 54)
Surely those who believe and do deeds of righteouness - unto them the All-merciful shall assign love. ( Maryam,19:96)
And He has sent between you love and compassion. (ar-Rum, 30: 21)
From what we have been told from hadith, the spirit and essence of religion is nothing but love. Burayd al-`Ijli said: "I was in the presence of Imam al-Baqir (as), and there was a traveller from Khurasan who had traversed that long journey on foot. He had the honour of meeting the Imam. His feet, which were showing through his shoes, were cut, and he had taken his shoes off. He said: "By God, the only thing that brought me from whence I have come is love of you, the Household (of the Prophet)." The Imam said: "By God, if a stone loved us, God would unite it with us, and join it to us. Is the religion other than love?" 
A man said to Imam as-Sadiq (as): "We have named our children after you and your fathers; will this action be of any benefit to us?" He said: "Yes, by God; is the religion other than love?" Then he gave the verse If you love Allah, follow me, and Allah will love you as evidence. 
Basically, it is love which brings obedience: the lover does not have the power to refuse the wishes of the one he loves. We have seen this with our own eyes when a youth who was in love left everything when faced with his loved one, his beloved, and sacrificed everything for her.
The obedience and worship of God is in proportion to the love which man has for God, as Imam as-Sadiq (as) said: "Disobey God and show that you love Him; by my life, that is something amazing. If your love were true, you would have obeyed Him, for the lover is submissive before the one whom he loves."
. Adapted from Nicholson's translation of Rumi, Mathnavi, bk. 1
. Ibrahim, 14:37
. ash-Shura, 42:23
 Safinatu 'l-bihar, vol.l, p.102 (under Hubb).
. ibid, p.662 (under Sama)