A New Testament writer may ascribe a prophetic meaning to an Old Testament passage. If the plain sense makes good sense, seek no other sense. The writers of The Bible wrote in a manner that would be understood by the people to whom it was written, therefore, interpret the meaning of a word in the same way it was written. The promises in scripture are available, but not necessarily for the believers of every generation. Some promises were made to specific people, or groups of people.
Many promises are conditional.
God is not bound to a conditional promise until that condition is satisfied. They must include everything that The Bible says on the subject. Scripture interprets scripture. Dig for deeper meanings, look up other passages that relate to the same subject. Do not build a doctrine on an obscure passage.