It is narrated from Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) that the case of the inheritance of a Jew whose heir was a Muslim was brought to him, and he said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Islam only increases (in good and blessing); it does not decrease." This hadith has a sahih (authentic) chain of narration, but the two Shaykhs (Bukhari and Muslim) did not record it.