First off, please be aware that Rumi's poetry is very often very poorly translated from the original Persian; the original meaning is often totally changed or lost in the English version. I found a couple of detailed articles about this online; it's very much worth the time to at least skim through these, check out their examples of Rumi poems with literal translations and published English 'translations'. To quote from the second link:
Yet this popularization has had a price, and the price is a frequent distortion of Rumi's words and teachings which permeate such well-selling books. The English "creative versions" rarely sound like Rumi to someone who can read the poems in the original Persian, and they are often shockingly altered-- but few know this, and the vast majority of readers cannot but believe that such versions are faithful renderings into English of Rumi's thoughts and teachings when they are not.
I don't know where, or in what language, you read the quote that you're looking for. But I'm pretty sure you didn't read it in Persian, since in the original version of your question you seemed unaware that Rumi's poems were even written in Persian! However, I did find that this quote has been attributed to Rumi on the English-speaking internet, see for example here. If indeed you found it in English, then it's quite possible that in fact Rumi never said anything like this. Or at least that the quote has been heavily distorted, so we should be looking for near misses as well as these exact words.
All of that being said ... I found a couple of websites which may be more reliable when it comes to Rumi poems. One of them is the site I quoted above
- they at least take pride in publishing proper translations of Rumi poems, rather than popular mistranslations/retellings. Another site
I'm less sure about (would have to get a Persian speaker to verify the accuracy of the translations), but at least they seem to take Rumi and his works pretty seriously. Searching those sites specifically
"soul of the universe"
turned up nothing, but searching for
"soul of the soul"
was at least a little more fruitful:
you worry too much.
You are in truth
the soul, of the soul, of the soul.
You are the security,
the shelter of the spirit of Lovers.
From "You Worry Too Much". Not an exact match, but it's about "the soul of the soul" and mentions love. (Translated by Shahram Shiva, whom Dar-Al-Masnavi cites as a semi-reliable translator.)
The drunkenness of love makes me unaware whether I have
profit [or] loss therefrom.
Thanks be to Him who gives soul to the body; if the soul
should depart, yet I have the soul of the soul.
Seek from me that which Shams-e Tabrizi has bestowed, for
I have the same.
From "I Have Fire For You". Again not an exact match, but it's about "the soul of the soul" and seems to imply that this equates to love. (Translated by A. J. Arberry, whom Dar-Al-Masnavi says is reliable.)
The mystical concert is tranquillity for the souls of the
(spiritually) alive ones; a person knows (this) who is the Soul of
Especially (if) they continue to make a circle in the mystical
concert and the Ka`ba is in the center.
From Jalâluddîn Rûmî, Dîwân-é Kabîr, Ghazal 339. Accurate/literal translation mentioning the "soul of the soul".
Some other hits for
"soul of the soul" love in Rumi poems. It looks like there's no exact match for your quote, but maybe one of the above was mistranslated/retold in that way?