But I say to you: do not swear at all, neither by heaven, because it is God’s throne,
Jesus raises the standard of the Old Covenant commandment, completely rejecting the practice of swearing by which people tried to add false assurance to their word. He teaches that a believer’s speech must be so truthful that there is no need for any oath. The phrase, “Not by heaven, because it is God’s throne,” shows that even everything people use as a basis for an oath belongs to God; therefore no one has the right to make it a guarantee for his own words. Thus Christ calls us to purity of speech and inner honesty, because the truth does not require the outward confirmation of an oath.