This ‘most’ difficult part of Christianity has given rise to many traditions of men and perversions of the Gospel.
The one that understands that statement, has the closest understanding of His Word which is actually revealed in the Bible itself (let ‘Scripture interpret Scripture’) as follows:
(i) The Blessed Lord Himself instructed to ‘keep the commandments’ to enter into ‘life’ (or, age-during life, i.e. ‘life in the coming age’):
“Why do you ask Me about what is good?” Jesus replied, “There is only One who is good. If you want to enter life, keep the commandments.” (Matthew 19:17)
(ii) Christians are aware that there are so many commandments in the Bible where some of which does “not” apply under the New Testament age (for example, circumcision as it’s described below):
In the Old Testament, it’s commanded even ‘before’ the Law of Moses as the Covenant between God & Abraham (and to Abraham –> and to ‘all Jews’ only):
“God said further to Abraham, “Now as for you, you shall keep My covenant, you and your descendants after you throughout their generations. “This is My covenant, which you shall keep, between Me and you and your descendants after you: every male among you shall be circumcised. “And you shall be circumcised in the flesh of your foreskin, and it shall be the sign of the covenant between Me and you.” (Genesis 17: 9 – 11)
This Covenant is “not” eternal as the Jews have greatly erred but only to that “age” (which ended in Christ) in this same chapter too:
“and God saith, ‘Sarah thy wife is certainly bearing a son to thee, and thou hast called his name Isaac, and I have established My covenant with him, for a covenant age-during, to his seed after him.” (Genesis 17:19)
This time period of “olam or owlam” proved true to be “age-during” only (not forever as so commonly mistranslated) as Scripture itself “proves” its own ‘meaning’ (via usage) to it (beyond the false definitions given by lexicographers, ironically of their own ‘mother tongue’) when we see that circumcision is “abolished” in Christ (under the New Covenant in this New Testament age):
“For in Christ Jesus neither circumcision nor uncircumcision means anything, but faith working through love.” (Galatians 5:6)
“Behold, I Paul say to you that if you shall become circumcised, Christ will profit you nothing.” (Galatians 5:2)
Remember, God did “not” change for He did “not” instruct an ‘everlasting covenant’ to Abraham which begins with ‘circumcision’ but rather “an age-during one” (limited time) which is proven by that ‘most important act of circumcision’ itself is nullified and means ‘nothing’ after its ‘fulfillment in Christ’ (especially spiritually as the “New” Covenant verses reveal as mentioned above).
(iii) Regarding the “Law of Moses” (not the age-during covenant given to Abraham as described a little above), this issue is discussed in detail in Acts 15 and a link to its conclusion of “what commandments” to keep with respect to the “Law of Moses” may be seen in this links below:
Where the conclusion is (what parts of the ‘Law of Moses to keep?’ – Nothing more is “added” in Scripture – a concluded matter!):
“You are to abstain from food sacrificed to idols, from blood, from the meat of strangled animals and from sexual immorality. You will do well to avoid these things. Farewell.” (Acts 15:29)
Yup, the ‘Old Covenant’ is gone and is thus replaced by the ‘New Covenant’ as the author of Hebrews spoke to the Jews even back then:
“in the saying ‘new (covenant),’ He hath made the first (covenant) old, and what doth become obsolete and is old is nigh disappearing.” (Hebrews 8:13)
‘Law of Moses’ is a ‘priesthood’ based observance and its duration is mentioned (regarding its performed rituals and feast observations or sabbath day activities) as ‘age-during’ only (not forever or everlasting) as these verses reveal:
“and anointed them as thou hast anointed their father, and they have acted as priests to Me, and their anointing hath been to be to them for a priesthood age-during, to their generations.‘” (Exodus 40:15)
“And this day hath become to you a memorial, and ye have kept it a feast to Jehovah to your generations; — a statute age-during; ye keep it a feast.” (Exodus 12:14)
“and the sons of Israel have observed the sabbath; to keep the sabbath to their generations is a covenant age-during,” (Exodus 31:16)
agreeing ‘perfectly’ in that “no” need to observe the “ritualistic aspects” of these (meaning of ‘let no one judge you’) under the New Covenant during this current New Testament age too as apostle Paul describes ‘so clearly’ in the verse below:
“Let no one, then, judge you in eating or in drinking, or in respect of a feast, or of a new moon, or of sabbaths,” (Colossians 2:16)
*Note that the “Law/custom of Moses” and “Covenant to Abraham” are both stated as “age-during” (limited time only as the verses above clearly ‘define’ this time period as quoted above too literally, see Genesis 17:19, Exodus 40:15, Exodus 12:14, Exodus 31:16 etc. with Hebrews 8:13 to ‘understand this’).
(iv) Next, how about the “Ten Commandments?”
It is to be ‘kept’ because it’s different in definition from the “Law/custom of Moses” and “Covenant to Abraham” which are both stated as “age-during”.
Note that the first definition of the “Ten Commandments” do NOT include any ‘time frame’ (age-during observance or otherwise) in Exodus chapter 20. This means that the “Ten Commandments” is NOT a time-bound observance, meaning it’s “always” to be observed across both the Old Testament or the New Testament age!
That’s why we ‘keep/obey’ the “Ten Commandments” (for example, the ‘Sabbath’ by ‘keeping it holy’ and ‘resting’ as Commanded minus all the ‘later law of Moses ritualistic additions to it’ —> keeping the Sabbath in its ‘first definition’ only).
(v) With these background, we may better understand Christ’s Blessed words when He said that ‘If you want to enter life, keep the commandments‘ (Matthew 19:17).
That’s why upon hearing this, the young man (knowing that there are so many commandments), asked, “which ones?” to which our Saviour replies ‘only quoting parts from the Ten Commandments” further validating point (iv) above! (He adds a ‘love command’ from Leviticus 19:18 too – that’s all).
Indeed, here are the verses (‘proof’) from Holy Scripture:
“Which ones?” he inquired. Jesus replied, “ ‘You shall not murder, you shall not commit adultery, you shall not steal, you shall not give false testimony, honor your father and mother,’ and ‘love your neighbor as yourself.’” (Matthew 19:18 – 19)
In conclusion, that’s what it means to “obey Him” (only those commandments that are valid under the New Testament Scripture):
“If you love Me, keep My commands.” – Lord Jesus Christ (John 14:15)
and it also means to fulfill the ‘doctrine of Christ’ (Inclusive of His Revelation of Doctrine in ‘all truth’ too):
“Whosoever transgresseth, and abideth not in the doctrine of Christ, hath not God. He that abideth in the doctrine of Christ, he hath both the Father and the Son.” (2 John 1:9)
Remember that trying to ‘keep the WHOLE LAW’ only “cuts-off one from Christ (estranges, severed – NOT bring you closer to Him as commonly erred)” —> resulting in “falling from Grace” as these verses describe:
“And I testify again to every man who receives circumcision, that he is under obligation to keep the whole Law. You have been severed from Christ, you who are seeking to be justified by law; you have fallen from grace.” (Galatians 5:3 – 4)
Read ‘carefully’ each point above and please make a ‘wise decision to understand His Truth correctly (with verses and not ‘traditions or oral explanations’ which are NOT found in Holy Scripture –> as opposed to the “sound” arguments with Scripture above).
Who will be able to do so?
“Jesus answered and said to him, “If anyone loves Me, he will keep My word; and My Father will love him, and We will come to him and make Our abode with him.” (John 14:23)
*You can’t keep a command (or His Word) if you didn’t understand it first.
“And this is love, that we should walk according to His commandments. This is the commandment, just as you have heard from the beginning, so that you should walk in it.” (2 John 1:6)
**Lawless acts with or without the Law will not be entertained by the Lord, even those ones done in “His Name”:
“And then I will declare unto them, ‘I never knew you; depart you from Me, those working lawlessness.” – Lord Jesus Christ (Matthew 7:23)
Is it possible to ‘be lawless’ with the ‘law’? Consider:
“For if I rebuild what I have once destroyed, I prove myself to be a transgressor. “For through the Law I died to the Law, so that I might live to God. ” (Galatians 2:18 – 19)
Yup, some will be found ‘guilty’ instead due to trying to keep the ‘WHOLE LAW’ as this verse describes too:
“For whoever keeps the whole law and yet stumbles in one point, he has become guilty of all.” (James 2:10)
Finally, those that “keep His Commandments” enter into life as described below too:
“Blessed are those who do His commandments, that they may have the right to the tree of life, and may enter in by the gates into the city.” (Revelation 22:14)