Explain the quote 'God sees everything'

In context, this quote illustrates the belief that God looks down in judgement upon everyone, just as Wilson judges his wife.

"I spoke to her," he muttered, after a long silence. "I told her she might fool me but she couldn’t fool God. I took her to the window" – with an effort he got up and walked to the rear window and leaned with his face pressed against it – "and I said ‘God knows what you’ve been doing, everything you’ve been doing. You may fool me, but you can’t fool God!’"

Standing behind him, Michaelis saw with a shock that he was looking at the eyes of Doctor T. J. Eckleburg, which had just emerged, pale and enormous, from the dissolving night.

"God sees everything," repeated Wilson."I spoke to her," he muttered, after a long silence. "I told her she might fool me but she couldn’t fool God. I took her to the window" – with an effort he got up and walked to the rear window and leaned with his face pressed against it – "and I said ‘God knows what you’ve been doing, everything you’ve been doing. You may fool me, but you can’t fool God!’"

Standing behind him, Michaelis saw with a shock that he was looking at the eyes of Doctor T. J. Eckleburg, which had just emerged, pale and enormous, from the dissolving night.

"God sees everything," repeated Wilson.