To discuss Bible doctrine gets you absolutely nowhere. It is impossible to arrive at a comprehensive understanding of it because the Bible is not a coherent set of texts, they were never written with the intention of becoming "The Holy Bible". It is an anthology, a careful selection modified to support a political ideal. Nothing fits properly unless you happen to know what was meant at the time of writing and the contemporary cultural milieu. The Bible is not divine, it was written and compiled for humans by humans.
However, the partisan writer of the text in question at John 2; 21,22 clearly had in mind a universal trope of pagan tales that demigod heroes died for three days and came back to life. (Ulysses did in the Odyssey)
The idea is drawn from the astronomical relevance of the "death of the Sun" December 21st when the point of sunset stops travelling south along the western horizon and "comes back to life" by starting to travel north three and a half days later at sunrise in the east on the 25th December. Three and a half days crops up a lot in the Bible as a signal of special meaning to "those in the know".
Nobody could have possibly remembered Jesus' words verbatim which became part of the the book of John. The words instead are the work of the promoters of the Jesus cult, who were in competition with other Christ cults all striving for market dominance in the first three centuries of the common era.
The readers back in the time they were written would have been led to understand that the cultural motif implied their man Jesus was no ordinary punter. Three days dead and a trip back to life makes you a God like the Sun God and his father. Such is the stuff of myth and mind bending propaganda.