Mu'jam Kabir Tabarani 10982 — the Prophet ﷺ said: Were it not

It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) said: "Were it not that the Black Stone has been defiled by the impurities and filth of the Jahiliyyah and by the hands of the oppressors and sinners, cure would be sought through it from every ailment, and it would have remained today in the very state in which Allah created it. Allah changed it to black only so that the people of this world would not look at the adornment of Paradise, and it will surely return to it. It is a ruby from the rubies of Paradise, which Allah placed when He sent Adam (peace be upon him) down at the site of the Ka'bah, before the Ka'bah existed. At that time the earth was pure; no sin had been committed in it, and it had no inhabitants who would make it impure. So a row of angels was appointed for it on the boundaries of the Haram, guarding it from the inhabitants of the earth (of that time), and its inhabitants at that time were the jinn. It was not fitting for them to look at it, because it was something from Paradise. So the angels kept them away from it, standing on the boundaries of the Haram and surrounding it from every side. That is why it was called the 'Haram', because they stood as a barrier between them and it."