'Cannot' in the Bible

Indeed, I have received a command to bless; he has blessed, and I cannot reverse it.

If Balak would give me his palace full of silver and gold, I cannot go beyond the commandment of the Lord to do either good or evil of my own will, but whatever the Lord tells me I must speak'?

everything that may stand the fire, you are to pass through the fire, and it will be ceremonially clean, but it must still be purified with the water of purification. Anything that cannot withstand the fire you must pass through the water.

"Whoever kills any person, the murderer must be put to death by the testimony of witnesses; but one witness cannot testify against any person to cause him to be put to death.

"You must not pollute the land where you live, for blood defiles the land, and the land cannot be cleansed of the blood that is shed there, except by the blood of the person who shed it.