the cross is the expression of the foundations of YAH's throne and Rulership which are Justice and Righteousness.
Psalm 89:14 Righteousness and justice are the foundation
of Your throne. Mercy and truth go before Your Face.
the cross is a picture of His Righteousness (the pole planted in the ground) and His Justice for His creation (the cross member). Isaiah portays a picture of it.
Isaiah 28:16 Therefore thus says the 'Adonay YHVH (H3069), “Behold, I lay in Zion for a Foundation a Stone, a tried Stone, a precious Cornerstone of a sure Foundation. He who believes shall not act hastily. 28:17 I will make justice the measuring line, and righteousness the plumb line. The hail will sweep away the refuge of lies, and the waters will overflow the hiding place. 28:18 Your covenant with death shall be annulled, and your agreement with Sheol shall not stand. When the overflowing scourge passes through, then you will be trampled down by it.
it is described in Romans.
Romans 3:21 But now apart from the law, a righteousness of YAH has been revealed, being testified by the Torah and the Prophets; 3:22 even the righteousness of YAH through faith in YAHSHUA the Messiah to all and on all those who believe. For there is no distinction, 3:23 for all have sinned, and fall short of the glory of YAH; 3:24 being justified freely by His grace through the redemption that is in Messiah YAHSHUA; 3:25 Whom YAH set forth to be an atoning Sacrifice through faith in His blood, for a demonstration of His righteousness through the passing over of prior sins, in YAH’s forbearance; 3:26 to demonstrate His righteousness at this present time; that He might Himself be just, and the justifier of him who has faith in YAHSHUA.