What is the ruling of Islamic Sharia on a man marrying another woman without his first wife's knowledge?

The wife's consent is not a condition for polygyny, but it is good companionship to reassure her. The husband must be just among his wives, and whoever is not just will come on the Day of Resurrection with one side of his body leaning. Allah commanded to be content with one wife if the husband fears not being able to act justly.