مُسْنَدُ أَحْمَدَ
Musnad Ahmad 1593
Musnad Abu Ishaq Sa'd bin Abi Waqqas
It was narrated from Muhammad bin Sa"d that his father Sa"d said: The Messenger of Allah (ﷺ) came out to us, striking one hand against the other and saying: "The month is like this and like this,” then he held one finger down the third time.
Musnad Ahmad 1594Sahih (Darussalam) [, Muslim (1086)]