The Shadow or Christ

Only condemn what God condemns v16.
The outworking of pride towards God and others and the evils to be avoided - Only God ordained ordinances assist and compliment the true doctrine of the gospel - The need for a sensitive and a robust conscience.

The ordinances used by the heretics v16.
OT ordinances the heretics insisted upon, including ‘sabbath days'; the permanent ordinance of the Sabbath still to be observed though now without ceremonial accompaniment and changed to the first day of the week - the heretics lack of regard and grasp concerning redemption accomplished in choosing to disregard the Christian Sabbath or Lord's Day.

The shadow and the substance v17.
The contrast between the shadow and the one casting the shadow, which shadow the faithful in the OT saw and knew to be Christ - The heretics loved the shadow more than the substance betraying the fact that they never saw and loved Christ at all - We are to pray for the conversion of the Jews - All true religion is Christ-centred.