Musannaf Ibn Abi Shaybah 38654 — the first to do a thing, and who did

Ubaydullah bin Ibrahim said that the first to have pebbles spread in the Prophet's Mosque was Sayyiduna Umar bin al-Khattab (may Allah be pleased with him). When people raised their heads from prostration, they would shake off their hands. He ordered pebbles to be spread, so pebbles were brought from al-Aqiq and spread in the Mosque of the Prophet (peace and blessings be upon him).