I shot an arrow into the air,
It fell to earth, I knew not where;
For, so swiftly it flew, the sight
Could not follow it in its flight.

I breathed a song into the air,
It fell to earth, I knew not where;
For who has sight so keen and strong,
That it can follow the flight of song?

Long, long afterward, in an oak
I found the arrow, still unbroke;

And the song, from beginning to end,
I found again in the heart of a friend.

-Henry Wadsworth Longfellow

At first glance, an arrow and a song seem completely separated, and having little or nothing in common except the speed with which they both disappear. Yet by the third stanza, the relation between the two is cemented as both objects (that formerly had taken one stanza each) are discussed and compared, fused, in one stanza.
Just as an arrow is capable of wounding, destroying, so a song is capable of healing. And just as a friend is capable of restoring a song (providing healing, joy, understanding), so is a friend capable of causing spiritual hurt like the physical harm an arrow can inflict. Like an arrow must be deliberately released to hit its target, so must the wounds that hurt us most from friends be deliberate and intentional.
When one shoots an arrow, or shares a song, he doesn’t know exactly how that arrow or song will be received; when one offers the gift of friendship, he does not know how his offer will be received. In one sense, he is leaving himself vulnerable – as though he has shot his only arrow of defense and is now left open to whatever may be shot his way, or has bravely allowed another to listen to his most personal emotions and in doing so, made explicit what may be scorned or rejected.
The specific adjective ” still unbroke” in the third stanza seems to strongly imply that the speaker expected his arrow to be broken, and one could say, also did not expect to find his song “in the heart of a friend.”
Friendship and joy is risky business: we are often broken, and our songs are rarely recovered. Yet, with great risk comes great value. Therefore, once found, true friendship is worth all the risk. Two people are able to know and care for each other well enough to think and feel with one heart, to finish each others’ songs, inspire each others’ songs, and most difficult of all, preserve each others’ songs “from beginning to end.” That is most difficult because it requires unselfish giving, the willingness of one individual to keep the heart of their friend, the “song” or soul of that person’s very existence, without losing even one line.
I cannot help but connect the idea of friendship, songs, and arrows with the biblical characters David and Jonathan. Jonathan risked his very life to preserve David (the writer and singer of the Psalms, a master musician) from his own father’s jealous hatred, by shooting an arrow in warning to the hiding David. In a few years, after David had been on the run from Saul’s attempts to kill him, he happened across a sleeping Saul one night, but instead of killing him, David demonstrated respect for his God and his friend by simply taking the spear and water jug next to Saul. David and Jonathan both did their best to preserve the life and heart of each other. And in spite of the worst circumstances, separation, and incredible stress, they managed to turn something terrible into a joy-giving, life-preserving friendship.