Let's keep the Sabbath until last day-Matthew 24:20

Some people who don't keep Sabbath insist Jesus told to physical jews in Matthew 24:20.
They say this is the Jesus' commandment to the Jews when they will face the destruction of Jerusalem in A.D.70. So they insist Christians in this age don't have to keep the Sabbath anymore.

Matthew 24:20 Pray that your flight will not take place in winter or
on the Sabbath.

Here, Jesus told to Jews? No.
Whom he told this at that time?
This is reply of Jesus when his disciples asked this question.

Matthew 24:3 As Jesus was sitting on the Mount of Olives, the disciples came to him privately. "Tell us." they said,"when will this happen, and what will be the sign of your coming and of the end of the age?"
Who asked to Jesus?his disciples.

Furthermore,
Matthew24:9 "Then you will be handed over to be persecuted and put to death, and you will
be hated by all nations because of me.

Who is this people that persecute because of Jesus' name?
Physical Jews? No.
Christians.

This is reply about the question both what is the sign of Jerusalem destruction and the end of age. So flight in Matthew 24:20 was happened in the A.D.70, but Second accomplishment of prophecy will be happen in the last age.

Matthew 24:21 For then there will be great distress, unequaled from the beginning of the world until now-and never to be equaled again.

This means the last distress.
So Jesus said to us to pray this distress will not take place on the Sabbath. Because We must keep the Sabbath until the last day.
This precious and important service day, the Sabbath, was changed into Sunday Service by Constantinus in A.D.321.
Christ Ahnsahnghong came down to the earth for our salvation and he make let us know Sabbath.
Look at the Bible. We must Keep the Sabbath not Sunday service.