The Prophet ﷺ said that selling on credit against the offspring of an unborn camel is usury.
حدثنا محمد بن جعفر حدثنا شعبة عن أيوب عن سعيد بن جبير
عن النبي ﷺ أنه قال في السلف في حبل الحبلة ربا
Its chain of transmission is sahih. I have not found anyone who mentions this hadith except through Tirmidhi's allusion to it, for Tirmidhi (2:234) narrated from Qutayba from Hammad bin Zayd from Ayub from Nafi from Ibn Umar, that the Prophet forbade the sale of habl al-habala. He then said, "And on this subject there is also a report from Abdullah bin Abbas." He then said, "Shuba narrated this hadith from Ayub from Saeed bin Jubayr from Ibn Abbas. But Abdul-Wahhab Thaqafi and others narrated it from Ayub from Saeed bin Jubayr and Nafi from Ibn Umar from the Prophet, and this is more sahih."His commentator, when pointing to the hadith of Ibn Abbas, said, "Tabarani reported it in his Mujam, as mentioned by Zaylai," meaning what is in Nasb Raya (4:10), quoting from Tabarani through the route of Ibrahim bin Ismail bin Abu Habiba from Dawud bin Husayn from Ikrima from Ibn Abbas, that the Prophet forbade the sale of madamin, malaqih, and habl al-habala. He also mentioned that Bazzar narrated it in his Musnad as well, and it is found in Majma al-Zawaid (4:104), where it is likewise attributed to both of them.It is clear that this is different from what Tirmidhi was pointing to, for he was only referring to this hadith narrated by Shuba, whereas the hadith of Ibn Umar which Tirmidhi narrated was also narrated by the two Shaykhs and others, with the addition of an explanation of habl al-habala. It states that the people of pre-Islamic times used to trade in camel meat on the basis of habl al-habala, and habl al-habala means that a she-camel gives birth to what is in her womb, and then the one that was born becomes pregnant in turn. So the Prophet forbade them from doing that.See Muntaqa, 2792.