what does it mean? I will have mercy and not sacrifice

But go ye and learn what that meaneth, I will have mercy, and not sacrifice: for I am not come to call the righteous, but sinners to repentance.
Mat 9:13 KJV

Jesus gave an instruction here, we ought to pay attention to it. He gave us an assignment which many have never attempted to do, resulting in some strange behaviours we see in church today. We have not learnt what it means when He said "I will have mercy, and not sacrifice..." and just as it caused some mixed reactions towards Jesus, and consequently unbelief, and consequently damnation on the said people, it is still causing issues amongst church people today.

It's no joke, because Jesus repeated this thing in some chapters after:

*[[Mat 12:7]] KJV* But if ye had known what this meaneth, I will have mercy, and not sacrifice, ye would not have condemned the guiltless.

if ye had known... it means they still do not get it. so will you like to get this today?
So good to know...
now let's go...

what is mercy? what is sacrifice?

first note that mercy and sacrifice as used by Jesus are antonymous. mercy is NOT sacrifice, they are never compatible. they cannot go together.
now God says he will prefer mercy, to sacrifice. Are you following?

From the context Jesus used the word, we can derive its meaning as I love to do, don't depend on the language dictionary to do this for you. the writer of that dictionary might not be born again! the writer might be an atheist, who knows?

*[[Mat 12:7]] KJV* But if ye had known what this meaneth, I will have mercy, and not sacrifice, ye would not have condemned the guiltless.

...ye would not have CONDEMNED the guiltless. hmm...

so "sacrifice is what you hold on to when you CONDEMN the guiltless".
Did you get that?

sacrifice is what you hold on to when you CONDEMN the guiltless

Jesus just healed a man on Sabbath (law) and this was CONDEMNED. therefore anytime you condemn a man and disqualify him from healing (God's free blessing) because the law (Sabbath) forbids it, you have not "learnt what it means when he says I will have mercy and not sacrifice" Why? God has said He will "have mercy", not sacrifice. What's sacrifice? The requirement of the Law for purification or sanctification.

Whenever something tries to come to CONDEMN you before your Maker who has vowed to have mercy, don't entertain it. because There is therefore now no condemnation to them which are in Christ Jesus...  *[[Rom 8:1]] KJV*
Now, is Jesus saying "let my people sin as they want to?" certainly not! but mercy has rejoiced over judgment for men God is meeting! (James 2:13)

Mat 9:12-13
But when Jesus heard that, he said unto them, They that be whole need not a physician, but they that are sick. But go ye and learn what that meaneth, I will have mercy, and not sacrifice:for I am not come to call the righteous, but sinners to repentance.
(KJV)

this message is not to the accusers, but to you. Go and learn what it means "mercy, not sacrifice" as that's why Jesus the physician delights in sick people like you. So stop cancelling your programmes because you have sinned. Stop distancing yourself from holy assemblies because you feel you're guilty or unworthy. He's definitely not encouraging atrocious living, no! But self condemnation is not it either.neither can self effort get you above sin. God WILL have mercy and not sacrifice! Learn what it means now!