'Striking hands' was the ancient gesture sealing a financial guarantee — a surety or pledge. The warning here is against carelessly taking on financial responsibility for another person's debts. This does not prohibit all generosity, but warns against making binding financial commitments you cannot control or fulfil.
Memory phrase: Be wise about your promises.
Talk about it: Why is it important to only promise what you can keep?
Prayer: God, help me be careful and wise with every promise I make.