Seventeenth century science did not always produce an accurate knowledge of botany. This led St. Francis de Sales to make use of some very creative -- albeit inaccurate -- similies when comparing the spiritual life to examples found in nature. Perhaps one of the most endearing is that of the almond tree: he posited that if one were to take an almond, carve a word or a letter into it, and plant it in the ground the fruit of that tree would all bear the same emblem. We know from modern studies in biology and botany that this would not work. His point, however, is clear and it is not altogether different from our Lord's message in today's Gospel.
Jesus speaks in response to those who were overly concerned about the Jewish dietary laws. He declared all food clean and explained that "uncleanness" has its source in a person's heart and not in the food he eats. For if we nurture negative thoughts, hurt feelings, angry responses, etc., we are bound to manifest the negative energy in our actions and our words -- even if we ourselves are unaware of it. St. Francis de Sales' botanical example suggests that if we "plant" and nurture kindness in our hearts, then the fruit of our thoughts and feelings will be made manifest in good deeds and kind words. In many ways it is easy to nurture the negative feelings which arise in our hearts because they bring with them great energy; kind feelings or thoughts may not always come naturally, but they do have a way of displacing the negative energy. Let us ask for the grace to sow seeds of kindness in our hearts and for an abundant harvest of good fruit.
"If we remain close to the Savior, meditating on him and giving heed to his words, his actions and his affections we shall gradually, by the help of his grace, learn to speak, to act and will like him."
St. Francis de Sales