Allah said:

﴿وَبُعُولَتُهُنَّ أَحَقُّ بِرَدِّهِنَّ فِي ذَلِكَ إِنْ أَرَادُواْ إِصْلَـحاً﴾

(And their husbands have the better right to take them back in that period, if they wish for reconciliation.)

Hence, the husband who divorces his wife can take her back, providing she is still in her `Iddah (time spent before a divorced woman or a widow can remarry) and that his aim, by taking her back, is righteous and for the purpose of bringing things back to normal. However, this ruling applies where the husband is eligible to take his divorced wife back. We should mention that (when this Ayah 2:228 was revealed), the ruling that made the divorce thrice and specified when the husband is ineligible to take his divorced wife back, had not been revealed yet. Previously, the man used to divorce his wife and then take her back even if he had divorced her a hundred separate times. Thereafter, Allah revealed the following Ayah (2:229) that made the divorce only thrice. So there was now a reversible divorce and an irreversible final divorce.