I would like to know if the following is a Buddha quote or not:
“The root of suffering is attachment.”
This precise wording wasn’t familiar to me, and I’d assumed that it was an interpretation of Buddhist teaching rather than something the Buddha said himself, but there is a saying from the Pali canon, upadhi dukkhassa mūlanti, which means “Attachment is the root of suffering.” So this is a genuine canonical quote.
You’ll find it in this sutta, but translated by Thanissaro as “Acquisition is the root of stress.” His translations are rather idiosyncratic, and he regularly renders “dukkha” (pain, suffering, unsatisfactoriness) as “stress.”
In this translation of the same sutta it’s “acquisition is the root of suffering.”
Bhikkhu Bodhi’s translation (not available online, but in The Middle Length Discourses of the Buddha, page 868) has “attachment is the root of suffering,” although he sometimes has “acquisition” in place of “attachment,” in various repetitions of the phrase.
My Pali dictionary gives upadhi as “clinging to rebirth (as impeding spiritual progress), attachment (almost syn. with kilesa or taṇhā…).”
So attachment is the root of suffering” is a perfectly fine translation.
All the best,