Muawiya wrote to Abdul-Rahman bin Shibl, instructing him to teach the people what he had heard from the Messenger of Allah ﷺ. So he gathered them and said, "I heard the Messenger of Allah ﷺ say, 'Learn the Quran, and once you have learned it, do not be excessive about it, do not neglect it, do not eat by means of it, and do not seek to amass wealth through it.'"
حدثنا عبد الرزاق قال أخبرنا معمر عن يحيى بن أبي كثير
كتب معاوية إلى عبد الرحمن بن شبل أن علم الناس ما سمعت من رسول الله ﷺ فجمعهم فقال إني سمعت رسول الله ﷺ يقول تعلموا القرآن فإذا علمتموه فلا تغلوا فيه ولا تجفوا عنه ولا تأكلوا به ولا تستكثروا به
Its isnad is sahih. Zayd bin Salam bin Abu Salam Mamtur was mentioned before, and his grandfather is Mamtur Habashi al-Aswad, who is trustworthy, one of the Tabiin, and has mursal narrations. Here he explicitly names the narrator, and the hadith has already appeared at 15468 without its introduction.