See the open sky
Charles SpurgeonThis refers first to the rain. The Lord will give it in due time. Rain is the emblem of all those heavenly refreshments that the Lord is ready to bestow on His people. Oh, may we have a copious rain to refresh the inheritance of the Lord!
It seems that we think that the treasury of God can only be opened by a great prophet like Elijah, but it is not like that, because this promise is for all the faithful of Israel, and, indeed, for each one of them. O believing friend, "Jehovah will open his good treasure to you." You too can see the open sky, and reach out and take your portion, yes, and a portion for all your brothers around you. Ask for what you want, and it will not be denied you, if you remain in Christ, and His words remain in you.
You have not yet known all the treasures of your Lord, but He will open them for your understanding. You certainly have not yet enjoyed the fullness of the riches of the covenant, but He will direct your heart to His love and reveal Jesus in you. Only the Lord Himself can do this for you; but here is His promise, and if you diligently listen to His voice, and obey His will, His riches will be yours in glory through Christ Jesus.
Source: The Bank of Faith Checkbook. Translation by Allan Roman.
http://www.spurgeon.com.mx/chequera/meditames/mayo.pdf