Is it permissible for my husband to take me back after divorcing me via WhatsApp, saying: "You are divorced, divorced, divorced," knowing that he regrets this divorce?

If the husband intended divorce with the repeated mobile message, all divorces have occurred, and she is irrevocably divorced from him (baynunah kubra). She is not permissible for him unless she marries someone else out of genuine desire, and he consummates the marriage with her, and then he divorces her or dies, and her waiting period ends. This is the view of the majority of scholars. However, if he only intended to pronounce a single divorce, or repeated the wording for emphasis, or did not intend a specific number, then only one divorce occurs. If he had not divorced her before, and did not intend three divorces, he may take her back without a new contract or mahr as long as she is within her waiting period.