58 The participles ὑπάρχων (huparchōn) and εἰδώς (eidōs) are translated as causal adverbial participles.
59 Grk “one from the fruit of his loins.” “Loins” is the traditional translation of ὁσφῦς (osphus), referring to the male genital organs. A literal rendering like “one who came from his genital organs” would be regarded as too specific and perhaps even vulgar by many contemporary readers. Most modern translations thus render the phrase “one of his descendants.”
60 An allusion to Ps 132:11 and 2 Sam 7:12–13, the promise in the Davidic covenant.

In other versions

ESVEnglish Standard Version

Being therefore a prophet, and knowing that God had sworn with an oath to him that he would set one of his descendants on his throne,

NIVNew International Version (2011)

But he was a prophet and knew that God had promised him on oath that he would place one of his descendants on his throne.

CSBChristian Standard Bible

Since he was a prophet, he knew that God had sworn an oath to him to seat one of his descendants on his throne.

NLTNew Living Translation

But he was a prophet, and he knew God had promised with an oath that one of David’s own descendants would sit on his throne.

LEBThe Lexham English Bible

Therefore, because he was a prophet and knew that God had sworn to him with an oath to seat one of his descendants on his throne,

KJV 1900King James Version

Therefore being a prophet, and knowing that God had sworn with an oath to him, that of the fruit of his loins, according to the flesh, he would raise up Christ to sit on his throne;

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