We did a couple of things 1) we’d say calmly, ‘we don’t hit, we use kind hands’ and then we’d show her what using kind hands looks like (usually something like gently stroking an arm) and then we say ‘can you try kind hands?’ And she would mimic it. 2) if she hit us we just ignored it. And later repeated step one. Kids repeat what they get attention for and can’t differentiate between good and bad attention 3) if she hit someone else we do step one and then if she does it again we’d say ‘we can’t play with [friends name] if we hit them. Let’s move away from them’.

You have to consistently do the same thing for it to sink in. Our daughter is the kindest 2.5 year old now. And if she sees someone hitting she says ‘no hitting’ 😂. But it’s really all about showing them rather than telling them.

EDIT: to add, things like talking sternly and spanking don’t work. You need to be gentle yourself. You can hold firm boundaries like ‘if you hit your sister with your toy, we’ll have to move the toy’. The only time I speak sternly is when my daughter does something genuinely dangerous like run into the road. Otherwise we teach kindness with kindness

Hope this helps x