Philippians 4:19

‘And my God will supply every need of yours according to his riches in glory in Christ Jesus.'

So as they had supplied his need as a servant of God, they could now be sure that God would supply all their needs in accordance with His riches in glory in Christ Jesus. They would find that God too would be more than generous, and that was because by their generous attitude towards those in God's service they had proved themselves to be His people. Furthermore God's generosity would far outweigh theirs. For no greater riches could in fact be imagined than those described here, in which the source was ‘His riches in glory' given to them as those who were ‘in Christ Jesus'. All that He had in eternity would be available to them, in the same way as they were available to His Son, and this would include both material and spiritual blessing. They had thus made the best of bargains. By giving little they would receive much, and that of a heavenly nature.

And this would be so because the same God Who supplied his needs as previously described, continually supplies the needs of  all  His true people because they are in Christ. That is in fact what he has been emphasising all the way through the passage, that God supplies the deepest needs of His own, whether it be Paul or the Philippians, or whoever, if they are walking faithfully with Him.