Who is the speaker of “only trustworthy narrators should transmit from the Messenger ﷺ”?

Isnād as Part of Religion: Transmitter Competence, Fitnah, and Connected Transmission

• Saʿd b. Ibrāhīm
• Imam Muslim’s own independent statement
• A direct Prophetic hadith
• The earlier statement of Ibn Sīrīn