The foundation may be found in Scripture:
10 “For as the rain and the snow come down from heaven
and do not return there but water the earth,
making it bring forth and sprout,
giving seed to the sower and bread to the eater,
11 so shall my word be that goes out from my mouth;
it shall not return to me empty,
but it shall accomplish that which I purpose,
and shall succeed in the thing for which I sent it. (Isaiah 55 ESV)
The word goes from God and will accomplish its purpose.
Isaiah gives two examples from the natural world to illustrate how this happens:
- Rain and snow which water the earth
- Seed for the sower and bread to the eater
Both examples include a two-fold process; one which happens before the other. Rain waters the earth immediately; snow must melt. Seed is sown before it can be harvested and made into bread.
If the examples are taken literally, the second would be similar yet different and perhaps better. Where rain waters the earth when and where it falls, melted snow flows into rivers to be used for irrigation. Similarly seed is sown yet later bread nourishes or sowing seed is work yet eating bread sustains life.
Conclusion
The "dual fulfillment" of prophecy is better understood as how the word of the LORD works. When it is given to a prophet about something which is future, then there will be that which from a human perspective is seen as a dual prophecy.
The authenticity of one who speaks for YHVH also reflects a two-fold nature:
- A false prophet will speak things which do not happen (Deuteronomy 18:22)
- A prophet who states what will happen but uses the "fulfillment" to authenticate a message to lead people to worship gods other than YHVH. (Deuteronomy 13:1-5)
The second issue likely speaks to prophets who might better be termed "seers." That is, they can see one thing which is future, yet as it is not from YHVH there is no second event. On the other hand, the first fulfillment from one who truly speaks for YHVH will have the message authenticated as coming from YHVH by the first fulfillment. Thus, YHVH gives the people a first sign as evidence they have been given the authentic word of YHVH.
One who speaks for YHVH will not only have the authenticating first event, the content of the message will also be authentic as YHVH's. The content could also be authenticated by examining what YHVH has done and said in the past. So the prophet who correctly predicts something but uses that to lead people into violating YHVH's previous commands, could immediately be seen as a false prophet despite the accuracy of their prediction.