what is lacking bw the father and the son?
Despite living together for years, the father knows nothing of his son which means that it is silence and not comprehension nor companionship which is prevalent between them. In desperation, the father wishes that he would have liked his son to turn prodigal and then reunite with him, rather than drift away from him as he has. Had that been the case, he would have turned his sorrow into a new kind of love for his son, inspired by forgiveness. However, both "put out an empty hand/ Longing for something to forgive", but the gesture ends without any real communication taking place.