By myself I have sworn means God has sworn an oath by himself. To swear an oath is to make a serious promise. It involves calling down upon oneself a certain punishment or curse if the promise is not kept. Normally a person makes an oath with God as the witness, but since God has made the oath here, he swears by himself. In Hebrew the word translated By myself occurs before the verb for sworn. This sentence order emphasizes the seriousness of the oath, implying that God stakes his own reputation on keeping the promise he has made, so the whole line may be rendered “I have sworn on my own reputation.” Revised English Bible has “By my life I have sworn,” and Bible en français courant says “As true as I am God, I have sworn.” Another possibility is “On my own head I have sworn.” Some languages may be able to use an ideophone here to express the seriousness of the oath.

From my mouth has gone forth in righteousness is a parallel to the previous line. My mouth is an image for God himself. Some languages may prefer to say simply “I” (Revised English Bible). In righteousness indicates that what God has promised has been done “in all integrity” (New International Version). It is a solemn promise that he will keep. For the whole line Good News Translation has “My promise is true,” but this rendering is not forceful enough. A better model is “I have spoken with complete honesty.”

A word that shall not return describes God’s oath as a promise that he will not withdraw (compare 55.11). New International Version says “a word that will not be revoked” (similarly New Jerusalem Bible), and Bible en français courant has “[a promise] that I will not change.” Another possible model is “a word/promise that I will [definitely] keep.”

To me every knee shall bow, every tongue shall swear is the content of God’s promise. To me every knee shall bow means that all people will kneel before God to show him respect and to worship him. Knee is a figure of speech referring to the whole person. Good News Translation uses a nonfigurative expression, rendering the fourth line as “Everyone will come and kneel before me.” If the gesture of kneeling carries no meaning in the receptor-language culture, other possible models are “Everyone will come and kneel before me in respect/worship” and “All people will come and respect/worship me.”

Every tongue shall swear seems to be an incomplete clause. Most likely it means that everyone will swear an oath of allegiance to Yahweh. They will swear to follow him. Tongue is another figure of speech referring to the whole person. Good News Translation uses nonfigurative language again, rendering this line as “and vow to be loyal to me,” which expresses its meaning well.

For the translation of this verse consider the following examples:

• On my own life I have made a solemn promise,
I have spoken with full integrity
a word that I will not revoke:
‘Everyone will kneel before me
and swear to be loyal to me.’

• On my very life I have made a vow,
with absolute truth I have made this promise that will not fail:
‘Before me every knee will bow,
and every tongue will swear loyalty.’

Quoted with permission from Ogden, Graham S. and Sterk, Jan. A Handbook on Isaiah. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here .