Be Careful Little Eyes

For some unimaginable reason probably having to do with an education in Christian schools I was singing:

Be careful little eyes what you see
Be careful little eyes what you see
For your Father up above is looking down in love
so be careful little eyes what you see

My daughter Z sat listening and then said: Dad, why 'be careful little eyes what you see'?

Me: It just means, don't look at things you shouldn't look at.

Z: Like the sun.