This is one of those albums with an interesting history. The band deciding to release an album with single one-hour track, a departure from their previous album Holy Mountain which contained a series of shorter individual songs.

Of course their new record label didnt know what to do with it. From Wikipedia

Within a few weeks of signing with London, the A&R member who was negotiating with Sleep had been transferred and replaced. After sending the finished album to London Records, the label told Sleep that they were not going to release the album in its current format... ...Sleep refused to have the album released in any edited form which led to a deadlock between London and the band. The members of Sleep have mixed feelings whether the album should have been released in general. Cisneros felt it should not have been released, while Pike was content with its release, saying "We did all the work so why leave it sitting around?"

• Al Cisneros stated that smoking cannabis was important to the song's creative process: "I was really dependent on the space I got into when I was using it, and some of the lyrics are about that...The line, 'Drop out of life [with bong in hand],' was kind of a creed at that point."[7] The song was originally known and performed live under the title "Dopesmoker". After their tour, the group began to be interested in a Middle Eastern desert theme which led to Sleep referring to the song as "Jerusalem" during later practice sessions.*

Review Excerpts via Pitchfork

*But Dopesmoker is an infinitely explorable listen, the kind of record that will goad your attention through miniscule rabbit holes whether or not you're as stoned as the people who made it. Hakius' pulse is the constant carrot, then, filling the spaces when the band aggresses, forcing them forward when they pull back. He is a reminder to continue toward Nazareth.

...And that's perhaps what remains most impressive about Dopesmoker, especially hearing it again for the first time through yet another reissue: It's an hour of adventure and momentum, where the lumber and the repetition somehow always push ahead.

...no matter how much pressure London placed on them to make something more commercial than personal, Sleep sound as if their very existence depends upon the successful exercise of this weed ritual. In a sense, it's safe to say it did. This record's influence on substance, style, and simple ambition within heavy metal has long outlived the band that made it.*