“Good” is the word we use to describe whatever is "worthy of approval.”
When we say that God is good, we are really saying that Who He is, what He does, and what He says are worthy of His Own approval.
God's approval is the original and final standard of good, because He is absolute goodness and He knows Himself perfectly.
“Then Moses said, ‘I pray You, show me Your glory!’”
“And He said, ‘I Myself will make all My goodness pass before you, and will proclaim the name of the Lord before you . . ..’ But He said, ‘You cannot see My face, for no man can see Me and live!’” (Exod 33:18-20)
God understands Moses’ request to see His glory as a request to see Him. Explaining that Moses must not see His face, God complies with Moses’ request to see His glory (to see Him) by revealing His goodness. In revealing His goodness to Moses, God reveals Himself to him.
God and His goodness are one.
The essence of all that He approves is already recognized by Him in His Own character and actions.
The Law of God expresses and reflects His own goodness. God does not obey some cosmic law outside of Himself that judges Him. But God does obey a law. The law He obeys is the law of His Own character. He never acts in a way that is inconsistent with this law because He cannot be at odds with Himself or false to Himself. He always acts according to His own character, which is eternally, immutably, and intrinsically good.
“And Jesus said to him, ‘Why do you call Me good? No one is good except God alone’” (Mark 10:18).
(Spotlight 1, Lesson 9 in Doctrine 101: Learning about God)