When people say to me that they feel unworthy to be called into the body of Christ, I generally say, "Really? I could have sworn that you were worthy." The sarcasm generally hits home.
The key takeaway—as far as membership in the body of Christ is concerned—is the realization that our calling is in accord with the delight of God. It's not about us; it's about Him. It delights Him to lavish unworthies with grace. Well, unworthy people are the only ones upon whom grace can properly be called grace.
