Everything we possess comes to us stamped with the cross, bought with the blood that is precious above all estimate, because it is the life of God. Hence there is nothing that we have a right to pledge, as if it were our own, for the fulfillment of our word....
Our Saviour did not, however, forbid the use of the judicial oath, in which God is solemnly called to witness that what is said is truth and nothing but the truth. Jesus Himself, at His trial before the Sanhedrin, did not refuse to testify under oath. The high priest said unto Him, “I adjure thee by the living God, that thou tell us whether thou be the Christ, the Son of God.” Jesus answered, “Thou hast said” (Matthew 26:63, 64)....
If there is anyone who can consistently testify under oath, it is the Christian. He lives constantly as in the presence of God, knowing that every thought is open to the eyes of Him with whom we have to do; and when required to do so in a lawful manner, it is right for him to appeal to God as a witness that what he says is the truth, and nothing but the truth....
Everything that Christians do should be as transparent as the sunlight. Truth is of God; deception, in every one of its myriad forms, is of Satan.... It is not a light or an easy thing to speak the exact truth. We cannot speak the truth unless we know the truth, and how often preconceived opinions, mental bias, imperfect knowledge, errors of judgment, prevent a right understanding of matters with which we have to do! We cannot speak the truth unless our minds are continually guided by Him who is truth.
Through the apostle Paul, Christ bids us, “Let your speech be alway with grace” (Colossians 4:6). “Let no corrupt communication proceed out of your mouth, but that which is good to the use of edifying, that it may minister grace unto the hearers” (Ephesians 4:29). In the light of these scriptures the words of Christ upon the mount are seen to condemn jesting, trifling, and unchaste conversation. They require that our words should be not only truthful, but pure.
Those who have learned of Christ will “have no fellowship with the unfruitful works of darkness” (chap. 5:11). In speech, as in life, they will be simple, straightforward, and true; for they are preparing for the fellowship of those holy ones in whose mouth “was found no guile” (Revelation 14:5).—Thoughts from the Mount of Blessing, 66-69. RC 71
Christ will never abandon the soul for whom He has died. Pr 301
"But I say unto you, Swear not at all; neither by heaven; for it is God's throne: Nor by the earth; for it is his footstool: neither 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." Matthew 5:34-36 (King James Version)