1 CORINTHIANS 16
1 Corinthians 16:2
A PATTERN FOR GIVING
GIVING IS PLANNED - The first day of the week.
Of course, they were to set it aside until the offering would be received. Most churches receive the offering weekly. My wife, Dottie and I have discovered that our giving is best done when we plan it.
The Lord's money is taken out of our pay first!
GIVING IS PERSONAL - Every one of you.
GIVING IS PROPORTIONAL - As God has prospered.
You might want to point out that some only get paid once every month or every two weeks. They are to give when they receive it, and not to be concerned about the weeks when they do not give.
We are to give as God has prospered us. I personally believe that the Christian should begin his giving by tithing to the local church.
For more guidelines for giving, see 2 Corinthians 8-9. Especially pay attention to 2 Corinthians 9:6-11