Kierkegaard on the importance of universal love for neighbor-- to fulfill the command and to actually love friends and family effectively
I love that last sentence! The paragraph is too strong on "duty" for my tastes, but I like the point that being a "neighbor" is proved by showing mercy / being neighborly.
Christianity, however, dethrones feeling and good fortune and replaces them with the shall. The point at issue between the poet and Christ may be stated precisely in this way: romantic love and friendship are preferential, the passion of preference; Christian love, however, is self-renunciation’s love and therefore trusts in the you shall. According to Christ, our neighbor is our equal. Our neighbor is not the beloved, for whom you have passionate preference, nor your friend, whom you prefer. Nor is your neighbor, if you are well educated, the learned person with whom you have cultural affinity – for with your neighbor you have before God the equality of humanity...
...love your beloved faithfully and tenderly, but let love to your neighbor be the sanctifier in your covenant of union with God. Love your friend honestly and devotedly, but let love to your neighbor be what you learn from each other in the intimacy of friendship with God! Moreover, the person who does not see that his wife is first his neighbor, and only then his wife, never comes to truly love his neighbor, no matter how many people he loves...
Kierkegaard distinguishes between different sorts of love, arguing that love of neighbor is primary and should be universal-- even loving one's wife as a neighbor first. And by implication, if one does not generally love one's neighbor, then love for a spouse-- without that-- will be distorted, likely to be temporary, etc. In sum, "love your beloved faithfully and tenderly, but let love to your neighbor be the sanctifier in your covenant of union with God."