Is it forbidden for a wife to take money from her husband without his knowledge—due to her need and his failure to fully provide for her rights?

A husband must provide for his wife equitably. If he falls short in providing, the wife is permitted to take from his money, without his knowledge, what suffices her and her children equitably, based on the Prophet's (peace be upon him) saying to Hind: "Take what suffices you and your children equitably." However, anything exceeding what is needed and considered excessive by custom, taking it would be a sin.