The obvious answer was SELECT ROUTINE_NAME,ROUTINE_DEFINITION FROM INFORMATION_SCHEMA.ROUTINES, given I like to use the INFORMATION_SCHEMA whenever possible. This lead me to think was is the corresponding SHOW command. A quick manual search got me to SHOW CREATE PROCEDURE.
What was interesting was not this, but the list of other SHOW commands I didn’t know. I did not know about SHOW MUTEX STATUS, SHOW OPEN TABLES and SHOW PROCEDURE CODE for example.