“Again you have heard that it was said to them of old, ‘Thou shalt not forswear thyself: but thou shalt perform thy oaths to the Lord.’ But I say to you not to swear at all, neither by heaven, for it is the throne of God: nor by the earth, for it is his footstool: nor by Jerusalem, for it is the city of the great king: neither shalt thou swear by thy head, because thou canst not make one hair white or black. But let your speech be yea, yea: no, no: and that which is over and above these, is of evil.”
The Lord here brings forward His love of simplicity. In the Old Covenant, swearing gave a sort of gravity, a wind in the sails, of one’s words, but here Jesus desires for His people to stand on what the Holy Spirit enacts through them: “For he was teaching them as one having power, and not as the scribes and Pharisees” (Matthew 7:29). He wants you to speak as one that is confident, both in Him and in what He has made you into, that you may not have to call upon different elements or saints to be able to be heard: “meddle not with the names of saints, for thou shalt not escape free from them” (Ecclesiasticus 23:10). He wants you to speak not so much from what you’ve read but from what wondrous love you have encountered with Him. While St. Paul on occasion calls on the Lord to be his witness, this commandment pertains more to keeping yourself under control, for “In the multitude of words there shall not want sin: but he that refraineth his lips is most wise” (Proverbs 10:19). The habit of swearing is not good, for it shows a lightness of heart, and keeping yourself from it also removes you from temptation to perjury. Now, while the heavens and the things of the earth are here exalted by Jesus, He shows that they are not the things by which one is to make promises. Vows and oaths are to be taken with great prudence and measure, preferably under a spiritual director, but are beautiful gifts to God when they are done with measure. Such things are promises to God, a giving of some aspect of your life back to Him, that He may hold it in His gentle hands. Things such as the vows of poverty, chastity, and obedience are wedding vows, promises to a Beloved that you will keep to make Him happy. Thus, they are due to Him alone, and not bound by any of His created things. Finally, because you are to be so immersed in truth due to your love of Jesus, “I am the way, and the truth, and the life” (John 14:6), it comes as natural to be able to speak simply on what you know and to be able to simply acknowledge what you don’t. It is a beautiful wisdom, much extolled by the Lord, to make your speech brief and simple: “He that setteth bounds to his words, is knowing and wise” (Proverbs 17:27) because it keeps a greater guard on your heart. Furthermore, a listening ear is a tremendous gift: “If thou love to hear, thou shalt be wise” (Ecclesiasticus 6:34), for many want to open their hearts to someone that will be caring with it, and when you love truly and purely, you will be given this gift. Being able to receive the words of others, be they wisdom from those that are more learned, or the hearts of those that want to be heard, is both humble and compassionate, an attitude to take towards your neighbor that they may be loved.