If the husband does not take compensation for divorcing the wife: The scholars are in consensus that if a man divorces his wife without taking compensation for issuing the divorce, and there is no reason to make this divorce irrevocable, he can take his wife back during her waiting period. The consensus is transmitted by Ibn Qudaamah.
2. If the husband takes compensation for divorcing the wife: The four Madhabs agree that if a man takes compensation for divorcing his wife, the divorce is deemed irrevocable.