To keep one's covenant means to fulfill or honor a promise, agreement, or commitment that one has made. It refers to the act of remaining true and faithful to a pledge or promise that has been made, whether it be to another person or to a higher power. The phrase is often used in religious contexts, where it refers to the importance of keeping one's promises and commitments to God. In a broader sense, it can refer to any agreement or promise that is made and kept, as a sign of integrity and trustworthiness.