This hadith has been narrated by Anas with another chain of transmitters and with minor additions.
Sahih Muslim Book 5, Hadith 384
← Previous Hadith Never did I ace the Messenger of Allah (ﷺ) so much grieved (at the loss of a) small army as I saw him grieved at those seventy men who were called" reciters" (and were killed) at Bi'r Ma'una; and he invoked curse for full one month upon their murderers.

Sahih Muslim Book 5, Hadith 383 Next Hadith → Anas b. Malik reported that the Messenger of Allah (ﷺ) observed Qunut for one month Invoking curse upon Ri'l, Dhakwan, 'Usayya. those who disobeyed Allah and His Messenger (ﷺ).

Sahih Muslim Book 5, Hadith 385