What is the ruling of the Sharia on practicing sex for a divorced man who does not have the means to marry again?

Sexual intercourse is forbidden except with one's wife, or with a slave-woman (milk al-yamin) - which is not present now. For those who cannot afford marriage, they should fast, as it is a protection from immorality.

Adultery is one of the major sins that warrants multiplied punishment on the Day of Judgment, and there is no escape from it except through sincere repentance.