Deut 18:18 I will raise them up a Prophet from among their brethren, like unto thee [Moses], and will put my words in his mouth; and he shall speak unto them all that I shall command him. 19 And it shall come to pass, that whosoever will not hearken unto my words which he shall speak in my name, I will require it of him.
Matt 5:19 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.
Matt 5:20 - Matt 7:23 (Jesus' Sermon)
Matt 7:24 Therefore whosoever heareth these sayings of mine, and doeth them, I will liken him unto a wise man, which built his house upon a rock: 25 And the rain descended, and the floods came, and the winds blew, and beat upon that house; and it fell not: for it was founded upon a rock. 26 And every one that heareth these sayings of mine, and doeth them not, shall be likened unto a foolish man, which built his house upon the sand: 27 And the rain descended and the floods came, and the winds blew, and beat upon that house; and it fell: and great was the fall of it. 28 And it came to pass, when Jesus had ended these sayings, the people were astonished at his doctrine: 29 For he taught them as one having authority, and not as the scribes.
Clearly Jesus has authority from the Father to deliver commandments to men, of which they are accountable to keep - just like the ancient Israelites were required to keep the law as it came through the mediator Moses. But the new laws are not grievous as were the old (Acts 15:10, Matt 11:30, 1 Jn 5:3). The question is: "if people disobey or deny them, will they be excluded from the kingdom?" I believe the answer is yes. It's helpful to ask, if that is NOT what Jesus meant, what DID he mean? Did he mean the person who disregarded his commandments would face worldly trouble much like a person would if he built a house on sand? I think not. The earliest disciples all followed Jesus commandments to a "T" and they endured brutal persecution and shame in the world. It's much more consistent to understand Jesus warning as a grave one pertaining to the world to come.
Moreover, consider some of the apostolic writing in light of the scriptures quoted above...
James 4:17 Therefore to him that knoweth to do good, and doeth it not, to him it is sin.
James 5:12 But above all things, my brethren, swear not, neither by heaven, neither by the earth, neither by any other oath: but let your yea be yea; and your nay, nay; lest ye fall into condemnation.
1 Cor 10:12 Wherefore let him that thinketh he standeth take heed lest he fall. (note: same greek word "fall")
1 John 2:3 And hereby we do know that we know him [Jesus], if we keep his commandments. 4 He that saith, I know him, and keepeth not his commandments, is a liar, and the truth is not in him.
John 14:15 If ye love me, keep my commandments. 21 He that hath my commandments, and keepeth them, he it is that loveth me: and he that loveth me shall be loved of my Father, and I will love him, and will manifest myself to him. 24 He that loveth me not keepeth not my sayings: and the word which ye hear is not mine, but the Father's which sent me.
Jesus was a mediator of the New Covenant under which men would either rise or fall. Beware of teachers today who endorse antinomianism - for God hates iniquity and lawlessness (Hebrews 1:9, Psalm 5:5, Matt 23:28).
Thanks for the great question, Ratchet30!