What is the rule for affirming a pre-Islamic marriage between a non-Muslim man (Harbi) and a non-Muslim woman (Harbiyyah) after they embrace Islam, following consummation?

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Every relationship they believed to be a marriage is affirmed upon their Islam. This applies if the marriage was one where affirming it initially is permissible under Islamic law, such as marriage without a guardian (Wali). If they did not believe it to be a marriage contract, it is not affirmed.