To hide one's light under a bushel.
Still water runs deep.
To look for a needle in a haystack.
To catch somebody red-handed.
Rome was not built in a day.
Haste makes waste.
What is done by night appears by day.
To nourish(cherish) a snake(viper, serpent) in one's bosom.
Save a stranger from the sea, and he'll turn your enemy.
One man sows and another reaps.
One beats the bush, and another catches the birds.
Like father, like son