Are we sinful because I had intercourse with my wife after her menstrual bleeding had stopped on the fifth day, then blood came from her again an hour after intercourse?

The period of purity preceding the return of blood and its flow after an interruption is considered a valid period of purity. If the wife observes purity, either by dryness or by the emission of the white discharge, she must perform ghusl (definition) and pray. At that point, sexual intercourse is permissible. If the blood returns again, she must refrain from prayer and other acts until it stops, then she must perform ghusl and pray. There is no sin in the intercourse that occurred during the purity period interspersed within the menstruation.