Briefly, explain the relevance of the 144,000 Jewish witnesses in Revelation 7?

The 144,000 anointed Jewish witnesses in Revelation 7 are representative of the 12-Tribes of Israel who will fulfill what Israel failed to fulfill during Messiah’s First-Advent; that is, Elohim sanctified the children of Israel as messengers and caretakers of His divine words; Elohim sanctified the children of Israel as progenitors of Messiah via Jacob’s son, Judah; Elohim sanctified the children of Israel as progenitors and proselytizers of the New Covenant as proclaimed in Jeremiah 31;31-34 and Ezekiel 36:26-27; Elohim sanctified the children of Israel as servants of the Gospel and the Great Commission which was to be taught and provided to “every family of the Earth” as Israel was to be Elohim’s blessing and fulfillment of what Elohim had promised through Abraham and the coming Messiah in Genesis 12:3b; unfortunately, Israel rejected the New Covenant’s Gospel; Israel rejected their Messiah and murdered Him upon a tree via Pilate and demanded that Messiah’s blood be upon them and the children; Israel rejected the Great Commission; therefore, Elohim turned to the Gentile and gave the Great Commission, the Gospel, the New Covenant, to the Gentile and placed the children of Israel under judgment until the fullness of the Gentiles have entered the Kingdom of Elohim (Romans 11:25).

The 144,000 spoken of in Revelation 7 will be a belated fulfillment of what Israel was foreordained to be and the “remnant” of Israel that is saved through the Tribulation Era will be the “remnant” spoken of by Isaiah (Isaiah 10:22) and reiterated by Paul (Romans 9:27). Elohim will honor His covenants and promises made to Israel’s children; this, NOT for Israel’s glory but for the righteousness and holiness and faithfulness of Elohim as Elohim does not lie but does exactly as He has promised irrespective of Satan’s success among the defiled of humanity (Numbers 23:19). There will be a “remnant” of Israel’s children who come to faith in Messiah Jesus during and in the final days of the Tribulation Era.