For reference, here’s that verse, Matthew 5:18:

For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.

Thats the KJV, here’s a NKJV:

For assuredly, I say to you, till heaven and earth pass away, one jot or one tittle will by no means pass from the law till all is fulfilled.

Here’s a bunch of other translations:

https://biblehub.com/matthew/5-18.htm

Absolutely tons of branches/denominations use this to justify upholding whatever their particular interpretation of whatever law they perceive from the Old Testament, the Tanakh/Torah.

‘The law’ is literally what Torah means in Hebrew, the Torah is the first five books of the Old Testament, The Tanakh broadly is the entire Hebrew Bible.