Greater love hath no man, than he would willingly lay down his life for his friends.
That is not only a testament to love - it's a definition of the word 'friendship', and a call to what can be the supreme sacrifice in its name.
The question of what makes a friend is slippery. Common interests? I share common interests with lots of people whom I've met, and we're not friends.
Common values? Same story.
Friendship is something that comes from the heart, and something that embeds itself so deeply that removing it a something of a surgical intervention. It's something like love.
In fact, it is love. C.S. Lewis wrote about it in "The Four Loves", and phrased it exactly that way.
Friendship is something you can't walk away from. It exerts a call, across the years and across the miles, and can be a conversation taken up, exactly where you left off, after thirty years.
Some friendships are born of a single word, some take time to develop from what at first is disdain, dislike, or even hatred. Sometimes we hate things in others that, deep down, we recognize we need.
Does a true friendship need nurturing? Sure, but not as much as you may think. If it requires constant attention...it's not really friendship. It's neediness, on one side or the other.
The nurturing a friendship needs is to be there when you're needed, and having your friend know that you are, without question.
You can count on a friend.
Even unto death.