Legalistic is a term that is used as an excuse not to obey God. For example, when you talk to church goers, about honoring the Sabbath, they call you legalistic.
Legalism is when you do something, in such a way, that you develop a critical spirit of micromanagement to where the act becomes your god, rather than the God who told you to do the act. Someone who is legalistic will be so obsessed with the act that they neglect the weightier matters. For example, the Pharisees.
Matthew 23:23 What sorrow awaits you teachers of religious law and you Pharisees. Hypocrites! For you are careful to tithe even the tiniest income from your herb gardens, but you ignore the more important aspects of the law—justice, mercy, and faith. You should tithe, yes, but do not neglect the more important things.
People who adamantly oppose the Law of God will accuse Sabbath keepers of being legalistic, even before they know anything about how you keep the Sabbath holy. Just the fact that you honor the Sabbath makes you legalistic in their mind. They will also define your belief system as a works-based salvation. The spirit behind this resistance is not the Spirit of YAH, because the Spirit of YAH was actually given to us to help us obey His Law, not resist it.
Ezekiel 36:26-27 I will give you a new heart and put a new spirit within you. I will take away your heart of stone and give you a heart of flesh. And I will put My Spirit within you and cause you to follow My Laws and be careful to do what I tell you.
It’s the sin nature behind the resistance to YAH’s Law, not the Spirit.
Romans 8:7-8 For the sinful nature is always hostile to God. It never did obey God’s laws, and it never will. That’s why those who are still under the control of their sinful nature can never please God.
The Pharisees taught the Law, which is what they should be doing, but they possessed a critical spirit, and were heavily involved in legalism, which is what Messiah came to correct.
Critical Spirit: a negative, fault-finding attitude that focuses on condemning and tearing down others, rather than building them up.
Matthew 23:1-4 Then Jesus spoke to the multitudes and to His disciples, saying: “The scribes and the Pharisees sit in Moses’ seat. Therefore, whatever they tell you to observe, that observe and do, but do not do according to their works; for they say, and do not do. For they bind heavy burdens, hard to bear, and lay them on men’s shoulders; but they themselves will not move them with one of their fingers.
It was the legalisms and the critical spirit that put the heavy burdens on the people, not the Law itself. When we learn from Messiah, and follow His lead, He removes all the heavy burdens and the critical spirit from obedience, He didn’t remove the obedience. I want you to pay close attention to what Messiah is saying because, even though He removes the heavy laden caused by legalism, there is still a yoke and burden we must bear in following Messiah. In other words, we still obey the Law when we follow Messiah, just not with a critical spirit.
Matthew 11:28-30 Come to Me, all you who labor and are heavy laden, and I will give you rest. Take My yoke upon you and learn from Me, for I am gentle and lowly in heart, and you will find rest for your souls. For My yoke is easy and My burden is light.”
When you follow Messiah, in relation to the Sabbath, He says we are lord of the Sabbath. In other words, we decide what we do on the Sabbath, which will be influenced by our love for YAH and His way, not by a list of dos and don’ts that we carefully monitor in others.
Pay very close attention to what Messiah is teaching when He says, “The son of man is lord of the Sabbath.” The title, "son of man" is a term for people i.e. human beings.
Psalm 8:4 What is man, that You think of him, the son of man that You care for him?
When He says, "The son of man is lord of the Sabbath" He is referring to the disciples picking grain to eat on the Sabbath.
Mark 2:23-24 Now it happened that He went through the grain fields on the Sabbath; and as they went His disciples began to pluck the heads of grain. And the Pharisees said to Him, “Look, why do they do what is not lawful on the Sabbath?”...verses 27-28 Then Jesus said to them, “The Sabbath was made to meet the needs of people, and not people to meet the requirements of the Sabbath. Therefore, the son of man is lord, even over the Sabbath!”
Notice how He didn’t say, “The Sabbath was made for Jesus; therefore, Jesus is Lord of the Sabbath.” Think of all the legalisms that are lifted when you have control over your own actions on the Sabbath Day, and not religion.
Those who are dominated by their sinful nature will never understand the WAY. The Way, which is the life and teachings of Messiah, bring freedom in the Law, not freedom from the Law.
Acts 24:14 I admit that I worship the God of our ancestors as a follower of the Way, which they call a cult. I believe everything that is in accordance with the Torah and that is written in the Prophets.
People who are right with God, through the cross of Messiah, will obey God’s Law. That's how you know they are right with God.
Romans 2:23 Just to hear the Law does not make a man right with God. The man right with God is the one who obeys the Law.
Obeying God’s Law is the fruit that reveals whether a person is a child of God or a child of the devil.
1 John 3:10 So, now we can tell who are children of God and who are children of the devil. Anyone who does not live righteously and does not love other believers does not belong to God.
If your pastor says it’s okay to bring the youth group to the beach on Sabbath, but they are not allowed to swim, he’s being legalistic.
If your pastor says you must eat your food cold on the Sabbath, he’s being legalistic.
If your pastor says you can’t leave your house on the Sabbath, he’s being legalistic.
If your pastor calls you legalistic because you want to honor the Sabbath, he is being dominated by his sin nature.
Romans 8:5-8 Those who are dominated by the sinful nature think about sinful things, but those who are controlled by the Holy Spirit think about things that please the Spirit. So letting your sinful nature control your mind leads to death. But letting the Spirit control your mind leads to life and peace. For the sinful nature is always hostile to God. It never did obey God’s laws, and it never will. That’s why those who are still under the control of their sinful nature can never please God.
Does it please our heavenly Father when His children obey Him? Of course it pleases Him, just like it pleases our earthly fathers when we obey them.
Deuteronomy 28:1 Be faithful in obeying the Lord your God. Be careful to keep all His Laws which I tell you today. And the Lord your God will set you high above all the nations of the earth.
1 John 3:22 And whatever we ask we receive from Him, because we keep His commandments and do those things that are pleasing in His sight.
Colossians 1:9-10 For this reason we also, since the day we heard it, do not cease to pray for you, and to ask that you may be filled with the knowledge of His will in all wisdom and spiritual understanding; that you may walk worthy of the Lord, fully pleasing Him, being fruitful in every good work and increasing in the knowledge of God.

"They call you legalistic"