And then Paul taught them in the process to be disciplined and methodical in this generosity, not just spontaneous or impulsive. So when he was collecting gifts for the poor he wrote to the Corinthians, “Now concerning the collection for the saints. . . . On the first day of every week [each Sunday, not Saturday], each of you is to put something aside and store it up, as he may prosper” (1 Corinthians 16:1-2). For Paul, discipline and regularity went hand in hand with joy. God loves a cheerful giver. God loves to see that joy overflow with disciplined regularity.
John Piper
From the book “The Treasure Principle: Unlocking the Secret of Joyful Giving (Lifechange Books)”