‘But as the Lord has distributed to each man, as God has called each, so let him continue to walk. And so I ordain in all the churches.'
Here the position in which each man finds himself when he is ‘called' is seen as God's previous distribution to him within His general purposes. Thus he may accept his lot and continue to walk in that way. It will in no way affect his spiritual position before God, as long as it does not interfere with his personal obedience to God's commands..
The purpose here is not to restrict them to a particular station in life but to show them that from a spiritual point of view their station in life is unimportant. They need not be desperate to get out of it. But he is not saying that they should not get out of it if the opportunity arises. (Just as earlier the unmarried can marry or not as they see best before God).
‘And so I ordain in all the churches.' He wants the Corinthians to know that he is not restricting them more than he does the other churches. He treats all the same and requires the same of all. Furthermore he may have hoped that this would be an encouragement to them as they felt themselves acting in unison with their Christian brothers.