Which, according to Catholic Church, is the writing in Old Testament that Jesus is referring to in Jn 7:38? We read in Jn 7: 37-38:

&quot;On the last day of the festival, the great day, while Jesus was standing there, he cried out, “Let anyone who is thirsty come to me,  and let the one who believes in me drink. As the scripture has said, ‘Out of the believer’s heart shall flow rivers of living water.’”

Going back to Old Testament, we read at Isaiah 58:11:

&quot;And the Lord will guide you continually and satisfy your desire in scorched places and make your bones strong; and you shall be like a watered garden, like a spring of water, whose waters do not fail.”

See that the verses of Isaiah make a good match for Jn 7:38, not a perfect match though, in that the words `living water' are missing from Isaiah.
My question therefore is: Which, according to the Catholic Church, is the writing in the Old Testament that Jesus is referring to in Jn 7:38?
The Catholic Bible on NewAdvent.org says that there is no exact match in known scripture.
HOLY BIBLE: John 7 says this:

On the last and greatest day of the feast Jesus stood there and cried aloud, If any man is thirsty, let him come to me, and drink;
yes, if a man believes in me, as the scripture says, Fountains of living water shall flow from his bosom.[5]
He was speaking here of the Spirit, which was to be received by those who learned to believe in him; the Spirit which had not yet been given to men, because Jesus had not yet been raised to glory.
…
[5] ‘His bosom’; it is not clear whether this refers to the believer, or to our Lord himself; the old commentators are not agreed. In either case, it is impossible to trace these exact words in any passage of scripture as we have it; cf. however Is. 44.3, Zach. 13.1. Some would punctuate differently, with a full stop, instead of a comma, after ‘believes in me’.

That Jesus was paraphrasing the scriptural imagery is a reasonable conclusion, regardless of one's denomination.