1 Corinthians 9:14

Even so hath the Lord ordained that they which preach the gospel should live of the gospel (KJV)

Then: Nothing left to chance. Paul just states the conclusion. There can be no doubt what the Corinthians should believe about their responsibility in paying apostles. Baker (p. 133) calls this the ultimate argument - the teaching of Christ himself when he sent out 72 followers without purses or extra clothing. Their needs would be supplied by those who received the Word.

Now: "The Bible says" are the halycon words for believers in Christ. Understanding the Lord's teachings is the desire and goal of all followers. To teach as Paul taught means always giving priority to Christ's statements.

Extra Source: Cornerstone Biblical Commentary 1 Corinthians (William Baker), 2 Corinthians (Ralph Martin & Carl Toney), ed. by Philip Comfort. Carol Stream: Tyndale House Publishers, c2006.