When should a church collect money?

Why does the assembly collection customarily follow the Lords Supper?

"Upon the first day of the week let every one of you lay by him in store, as God hath prospered him" (1 Corinthians 16:2). This is a personal responsibility enjoined on each believer (not couple) in the assembly. Paul has in view, though, "the collection for the saints" (verse 1) and wants to avoid a "gathering" when he comes to Corinth (verse 2). He teaches, therefore, that on the first day of the week the believers should contribute to a collective fund. These communications (Hebrews 13:16) are sacrifices, a part of our worship. Offering up spiritual sacrifices is the first priority of our gathering, but we should not conclude our gathering without these material offerings - whether by passing a basket or contributing to a box conveniently located in the place we meet.

D. Oliver