It is only known to God; it is unknown to people.
Synonyms: I don't know, who knows
Don't touch that! God knows who else put their hands on that thing!
(often modifying a parenthetic concession) It is known unto God; it is certainly true.
Synonyms: certainly, of course, obviously
God knows many kids don't like going to school!
God tested Abraham. That is, he sent him afflictions for his benefit, not so that he could find out what sort of man he was, for God knows everything, but so that He give him the means to perfect his faith. Marcus Eremita
Whether I was in my body or out of my body I know not. God knows it! George Frideric Handel
There is no man on earth who can give a final judgment on what the most beautiful shape may be. Only God knows. Albrecht Dürer
God knows why he has made the wings of some birds shorter. Slovenian Proverb
The rooster said, "I shall cry but whether the sun rises God knows." Georgian Proverb
Man concocts a million schemes; god knows but one. Chinese Proverb