@Pluralis the scripture you're looking for is this:
17 Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.
"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.
19 Whosoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven." (Matthew 5:17-19)
This website is useful you can read lots of different translations and there are study resources.
https://www.biblegateway.com/
I can never quite work out whether he's upholding Jewish tradition or creating something new from the old prophecies.
I would say something new (but interpretations of this vary). By believing in Christ, what He has done for us, we receive His grace to do His will.
"10 By the which will we are sanctified through the offering of the body of Jesus Christ once for all.
11 And every priest standeth daily ministering and offering oftentimes the same sacrifices, which can never take away sins:12 But this man, after he had offered one sacrifice for sins for ever, sat down on the right hand of God;13 From henceforth expecting till his enemies be made his footstool.14 For by one offering he hath perfected for ever them that are sanctified.15 Whereof the Holy Ghost also is a witness to us: for after that he had said before,16 This is the covenant that I will make with them after those days, saith the Lord, I will put my laws into their hearts, and in their minds will I write them;17 And their sins and iniquities will I remember no more.18 Now where remission of these is, there is no more offering for sin." (Hebrews 10: 10-15)