13When God made a promise to Abraham, because he had no one greater by whom to swear, he swore by himself, 14saying, “I will surely bless you and multiply you.” 15And thus Abraham, having patiently endured, obtained the promise. 16Human beings, of course, swear by someone greater than themselves, and an oath given as confirmation puts an end to all dispute. 17In the same way, when God desired to show even more clearly to the heirs of the promise the unchangeable character of his purpose, he guaranteed it by an oath, 18so that through two unchangeable things, in which it is impossible that God would prove false, we who have taken refuge might be strongly encouraged to seize the hope set before us. 19We have this hope, a sure and steadfast anchor of the soul, a hope that enters the inner shrine behind the curtain, 20where Jesus, a forerunner on our behalf, has entered, having become a high priest forever according to the order of Melchizedek. (Hebrews 6:13-20, NRSV)
God swore to Abraham by himself and on himself. We as humans sometimes do not take the word of others as truth and ask them to swear an oath on something greater than themselves.
But through God we are given a sure and certain hope and a promise that is sure.
So don’t swear by anything and know that God’s promise is firm. A solid foundation on which to build our lives.

35James and John, the sons of Zebedee, came forward to him and said to him, “Teacher, we want you to do for us whatever we ask of you.” 36And he said to them, “What is it you want me to do for you?” 37And they said to him, “Grant us to sit, one at your right hand and one at your left, in your glory.” 38But Jesus said to them, “You do not know what you are asking. Are you able to drink the cup that I drink, or be baptized with the baptism that I am baptized with?” 39They replied, “We are able.” Then Jesus said to them, “The cup that I drink you will drink; and with the baptism with which I am baptized, you will be baptized; 40but to sit at my right hand or at my left is not mine to grant, but it is for those for whom it has been prepared.” 41When the ten heard this, they began to be angry with James and John.42So Jesus called them and said to them, “You know that among the Gentiles those whom they recognize as their rulers lord it over them, and their great ones are tyrants over them. 43But it is not so among you; but whoever wishes to become great among you must be your servant, 44and whoever wishes to be first among you must be slave of all. 45For the Son of Man came not to be served but to serve, and to give his life a ransom for many.” (Mark 10:35-45, NRSV)
5Let the same mind be in you that was in Christ Jesus, 6who, though he was in the form of God, did not regard equality with God as something to be exploited, 7but emptied himself, taking the form of a slave, being born in human likeness. And being found in human form, 8he humbled himself and became obedient to the point of death— even death on a cross.9Therefore God also highly exalted him and gave him the name that is above every name, 10so that at the name of Jesus every knee should bend, in heaven and on earth and under the earth, 11and every tongue should confess that Jesus Christ is Lord, to the glory of God the Father. (Philippians 2:5-11, NRSV)
15What then? Should we sin because we are not under law but under grace? By no means! 16Do you not know that if you present yourselves to anyone as obedient slaves, you are slaves of the one whom you obey, either of sin, which leads to death, or of obedience, which leads to righteousness? 17But thanks be to God that you, having once been slaves of sin, have become obedient from the heart to the form of teaching to which you were entrusted, 18and that you, having been set free from sin, have become slaves of righteousness. 19I am speaking in human terms because of your natural limitations. For just as you once presented your members as slaves to impurity and to greater and greater iniquity, so now present your members as slaves to righteousness for sanctification.20When you were slaves of sin, you were free in regard to righteousness.21So what advantage did you then get from the things of which you now are ashamed? The end of those things is death. 22But now that you have been freed from sin and enslaved to God, the advantage you get is sanctification. The end is eternal life. 23For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord. (Romans 6:15-23, NRSV)
7For whoever has died is freed from sin. 8But if we have died with Christ, we believe that we will also live with him. 9We know that Christ, being raised from the dead, will never die again; death no longer has dominion over him. 10The death he died, he died to sin, once for all; but the life he lives, he lives to God. 11So you also must consider yourselves dead to sin and alive to God in Christ Jesus. 12Therefore, do not let sin exercise dominion in your mortal bodies, to make you obey their passions. 13No longer present your members to sin as instruments of wickedness, but present yourselves to God as those who have been brought from death to life, and present your members to God as instruments of righteousness.14For sin will have no dominion over you, since you are not under law but under grace. (Romans 6:7-14, NRSV)
What then are we to say? Should we continue in sin in order that grace may abound? 2By no means! How can we who died to sin go on living in it? 3Do you not know that all of us who have been baptized into Christ Jesus were baptized into his death? 4Therefore we have been buried with him by baptism into death, so that, just as Christ was raised from the dead by the glory of the Father, so we too might walk in newness of life. 5For if we have been united with him in a death like his, we will certainly be united with him in a resurrection like his. 6We know that our old self was crucified with him so that the body of sin might be destroyed, and we might no longer be enslaved to sin. (Romans 6:1-6, NRSV)
46While he was still speaking to the crowds, his mother and his brothers were standing outside, wanting to speak to him. 47Someone told him, “Look, your mother and your brothers are standing outside, wanting to speak to you.” 48But to the one who had told him this, Jesus replied, “Who is my mother, and who are my brothers?” 49And pointing to his disciples, he said, “Here are my mother and my brothers! 50For whoever does the will of my Father in heaven is my brother and sister and mother.” (Matthew 12:46-50, NRSV)