Paul elaborates on what the will of God is. Note the comma, which indicates equality of thought between these two phrases: "...the will of God, my sanctification." Anybody who thinks that Christianity is just about "knowing God" is mistaken. Our faith can't be boiled down or encapsulated. It's not necessarily complicated, but it's not 2 or 3 bullet points either. God's will is eternal and immutable and mysterious. And though knowing him is a grand and cosmic buffet to which every believer has access, we are also intended to grow in our sanctification.

1 Thessalonians 4:3