Rule with a rod of iron/with an iron hand phrase
To control a group of people in a very strict way
He is a very tough boss. He has ruled us with an iron hand.
The verb "rule" must be conjugated according to its tense.
This term comes from Tyndall’s translation of the Bible (1526): “And he shall rule them with a rodde of yron.” It was later transferred to any kind of stern domination, either serious or ironic.
If you fall for someone's trick the first time then they are at fault.
Are you going to mess with me again? Fool me once, shame on you; fool me twice, shame on me.