What is the reference for the proof Gödel's first incompleteness theorem based on the undecidability of the halting problem?
I believe that some version of this connection can be tied back to Turing's seminal paper on computability.

Namely, Turing makes the following two claims:


"The results of Section 8 have some important applications. In particular, they can  be used  to  show that  the  Hilbert Entscheidungsproblem can  have no solution."
"If the negation of what Godel has shown had been proved, i.e. if, for each $U$ either $U$ or $\neg U$ is provable, then  we should have an immediate solution of the Entscheidungsproblem."


The conclusion, I believe, follows from Modus Tollens.