The monthly sacrifices described here devolved into the New Moon feasts God later rejected in Isaiah 1:13-14:
13"Stop bringing meaningless offerings!
Your incense is detestable to me.
New Moons, Sabbaths and convocations--
I cannot bear your worthless assemblies.
14 Your New Moon feasts and your appointed festivals
I hate with all my being.
They have become a burden to me;
I am weary of bearing them."
God rejected the sacrifices He had commanded because they had become empty ritual. Instead of rending their hearts and turning from sin, the people treated the sacrifices as if they were a license to sin. The feasts that were intended to celebrate the goodness and generosity of God had become opportunities for debauchery and self-indulgence.
When we gather to worship, do we focus on repenting from the sin that impedes our fellowship with God or on where we are going for Sunday lunch? Do we treat lightly the sacrifice that God made once and for all to put an end to sin? God detested the mockery the Israelites made of the sacrifice of lambs and bulls. What will His wrath be toward those who mock the sacrifice of His Son by continuing to indulge in the sin that He died to free them from?
We are not perfect, and even after the blood of Christ has been applied for our salvation, we will still sin. Turning from sin is not about gaining perfection, but recognizing the price that was paid for our forgiveness.