According to a Feb 3, 2021 blog entry ("Why Is Marijuana Called Reefer?") of Kushfly, a medical cannabis company, Time Magazine published an article in 1931 explaining how to roll a "reefer", a cannabis-infused cigarette:
The term first appeared in print in 1931. An article printed in Time Magazine talked about how marijuana leaves could be dried, ground and than rolled into a ‘reefer cigarette,’ saying ‘These cigarettes are bootlegged under the name of ‘muggles,’ ‘reefer,’ or ‘Mary Warners.’
Did Time Magazine publish such an article? A search of Time's website under the Marijuana tag doesn't show it, but the earliest article under that tag seems to be from 2016 so it is likely that older articles are not tagged and/or not available on the website.