All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
A husband’s saying to his wife: “You are my mother and sister”, does not itself lead to divorce or Thihaar as this statement is not a clear statement of divorce or Thihaar. For the definition of Thihaar, please refer to Fatwa 85470.
Nonetheless, if the husband intended divorce or Thihaar by uttering such a statement; then what he had intended has taken place (i.e. has become effective). For more benefit, please refer to Fataawa 88080 and 83779.
If we presume that he intended to divorce his wife, then divorce has taken place and it is not a condition to have witnesses for divorce to become effective. Rather, having witnesses for divorce is desirable as discussed in Fatwa 133297.
If this divorce is not the third divorce, then the husband has the right to take back his wife without a new contract as long as she is still in her waiting period. If her waiting period has expired, a new marriage contract should be conducted. For more benefit, please refer to Fatwa 82541.
Finally, it should be noted that anger does not prevent divorce from taking place unless the person is unaware of what he is saying as discussed in Fataawa 121374 and 83467.
Allaah Knows best.