God chose the Israelites as His special people because He loved them (Deuteronomy 4:37, 10:15, Isaiah 43:1-4). The people were commanded to love God in return:
Hear, O Israel: The LORD our God, the LORD is one. Love the LORD your God with all your heart and with all your soul and with all your strength. (NIV, Deuteronomy 6:4-5)
That love was to be shown by serving God and obeying His commands (Deuteronomy 10:12-13, Joshua 22:5).
The Israelites were also commanded to have sincere good will for each other:
Do not seek revenge or bear a grudge against one of your people, but love your neighbor as yourself. I am the LORD. (NIV, Leviticus 19:18)
Related Verses: Genesis 24:67, 29:18-20, Deuteronomy 7:9, 1 Samuel 18:20, 2 Samuel 13:1, Psalms 31:23, Daniel 9:4
Agapao (verb) and agape (noun). This is the "Christian love" of the Bible. It means affection, benevolence, good-will, high esteem and concern for the welfare of the one loved. It is deliberate, purposeful love rather than emotional or impulsive love. Almost all of the New Testament references to love are agapao or agape in the original Greek language. The King James Version of the Bible sometimes translates agape as "charity," but charity has now taken on the meaning of assistance to the poor rather than benevolent love.
Phileo (verb). This means to love in an impulsive and emotional way. It is seldom used in the Bible, but there is a play on words (lost in English) in John 21:15-17. Jesus says to Peter, "Simon son of John, do you truly love (agapao) me?" Peter answers, "Yes, Lord, you know that I love (phileo) you." Philadelphia is a related word meaning the love of brothers or sisters (e.g., Romans 12:10). It is often translated "brotherly love."
All the references below are translations of agapao or agape except as noted.
God is love, and all who live in love live in God, and God lives in them. (NLT, 1 John 4:16)
Our relationship to God is like the loving relationship between a child and parent. Like a loving parent, God knows and cares deeply for each of us:
Are not five sparrows sold for two cents? And yet not one of them is forgotten before God. Indeed, the very hairs of your head are all numbered. Do not fear; you are of more value than many sparrows. (NAS, Luke 12:6-7)
Like children, some of us return God's love, and some do not. Nevertheless, He loves all of us. God's gifts of love and salvation are freely offered to all, even to those who choose the path of wickedness instead:
He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous. (NIV, Matthew 5:45)
Related verses : Matthew 6:25-30, 7:8-11, Luke 15:4-7, John 3:16-17, 16:27 (phileo), Romans 8:38-39
One of the teachers of the law came and heard them debating. Noticing that Jesus had given them a good answer, he asked him, "Of all the commandments, which is the most important?" "The most important one," answered Jesus, "is this: 'Hear, O Israel, the Lord our God, the Lord is one. Love the Lord your God with all your heart and with all your soul and with all your mind and with all your strength.' (NIV, Mark 12:28-30)
We demonstrate our love for God by obeying His commandments and Jesus' commandments (Luke 11:28, John 14:21-24, 2 John 1:6), putting our trust in Him (John 14:1), maintaining a humble attitude (Matthew 18:1-4, Luke 18:9-14), and by prayer (Matthew 6:9-13, Luke 18:1-8).
Related verses: Matthew 6:24, Matthew 7:2, 10:37 (phileo), Luke 6:46-49, Luke 11:27-28, Luke 18:15-17, John 6:28-29, John 6:66-69, John 12:44, John 14:15
The second is this, 'You shall love your neighbor as yourself.' There is no other commandment greater than these. (NRSV, Mark 12:31)
You have heard that the law of Moses says, "Love your neighbor and hate your enemy." But I say, love your enemies! Pray for those who persecute you! In that way, you will be acting as true children of your Father in heaven. For he gives his sunlight to both the evil and the good, and he sends rain on the just and on the unjust, too. If you love only those who love you, what good is that? Even corrupt tax collectors do that much. If you are kind only to your friends, how are you different from anyone else? Even pagans do that. But you are to be perfect, even as your Father in heaven is perfect. (NLT, Matthew 5:43-48)
If I speak in the tongues of mortals and of angels, but do not have love, I am a noisy gong or a clanging cymbal. And if I have prophetic powers, and understand all mysteries and all knowledge, and if I have all faith, so as to remove mountains, but do not have love, I am nothing. If I give away all my possessions, and if I hand over my body so that I may boast, but do not have love, I gain nothing. (NRSV, 1 Corinthians 13:1-3)
Love is patient; love is kind; love is not envious or boastful or arrogant or rude. It does not insist on its own way; it is not irritable or resentful; it does not rejoice in wrongdoing, but rejoices in the truth. It bears all things, believes all things, hopes all things, endures all things. Love never ends. But as for prophecies, they will come to an end; as for tongues, they will cease; as for knowledge, it will come to an end... And now faith, hope, and love abide, these three; and the greatest of these is love. (NRSV, 1 Corinthians 13:4-8, 13)
The passage above is often read at weddings, and it is especially applicable to marriage. Romantic feelings and sexual attraction may fade with time, but true unselfish Christian love for each other is the "glue" that can hold marriages together for a lifetime. Related article: What Does the Bible Say About Marriage, Divorce and Remarriage?
Let no debt remain outstanding, except the continuing debt to love one another, for he who loves his fellowman has fulfilled the law. The commandments, "Do not commit adultery," "Do not murder," "Do not steal," "Do not covet," and whatever other commandment there may be, are summed up in this one rule: "Love your neighbor as yourself." Love does no harm to its neighbor. Therefore love is the fulfillment of the law. (NIV, Romans 13:8-10)
God is the source of all our love. Loving God and loving other people are so interrelated that we cannot have one without the other:
We love because he first loved us. Those who say, "I love God," and hate their brothers or sisters, are liars; for those who do not love a brother or sister whom they have seen, cannot love God whom they have not seen. The commandment we have from him is this: those who love God must love their brothers and sisters also. (NRSV, 1 John 4:19-21)
Related verses: Leviticus 19:18, Matthew 5:21-24, 5:38-39, 6:14-15, 18:21-35, 22:34-40, 25:31-46, Luke 6:27-31, 6:38, 10:25-37, John 13:34-35, 15:9-13, Romans 12:10 (philadelphia), Galatians 5:13-15, 5:22-23, James 2:8-9, 1 Peter 4:8-10, 1 John 4:7-21