Eugene Peterson's Leap Over a Wall: Earthly Spirituality for Everyday People is a book about the story and life of David. One of Peterson's chapters is on the friendship of David and Jonathan.
He writes, "Friendship forms. Friendship is a much underestimated aspect of spirituality. It's every bit as significant as prayer and fasting. Like the sacramental use of water and bread and wine, friendship takes what is common in human experience and turns it into something holy."