Imam al-Shafi'i (may Allah have mercy on him) said: In the hadith of Ibn Abi Dhi'b there is evidence that Sayyiduna Sahl bin Sa'd (may Allah be pleased with him) said: "This became the practice for the two who perform li'an," while in the hadith of Malik and Ibrahim bin Sa'd it appears to be the statement of Ibn Shihab. There may be no contradiction in this: Ibn Shihab says it once without mentioning Sahl, and another time says it mentioning Sahl. And Ibn Abi Dhi'b agreed with Ibrahim bin Sa'd in the addition at the end of the hadith beyond the hadith of Malik.
Al-Shaykh (may Allah have mercy on him) said: As for the hadith of Ibn Abi Dhi'b, it is as follows.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب اللعان / 15315