Some early 14th Passover advocates assert that the conjunction "waw" used in Numbers
28:4 indicates a definite, immediate, future, and chronological order.  Some Hebrew
researchers tend to err because of their overall lack of understanding the language and
because of their doctrinal bias.  According to one Rabbi, the "waw" throws what went
before it into the future.  The idea that the “waw” throws what went before into the
<immediate> future is false.  The "waw" throws what went before into the indefinite
future unless the context of the verse, chapter, book, or bible shows how far into the
future that is.  “Between the evenings” establishes the future for “waw” as far as the
evening sacrifice and the Passover are concerned.

Chronological order: Arranged in order of time of occurrence.  Chronological order
indicates a certain sequence of events.  The writer must specify the time of those events
as well as their sequence in order for us to know when those events take place.  

Notice the chronological order of this verse:  1) Keep it up <until> the 14th day of the
month; 2) When (the sequence of the next act) the whole assembly killed it (the next act)
between the two evenings (the timing of the next act).  What the Rabbi and Hebrew
scholar says is that the "waw" throws the structure of the sentence into the future.  If
Moses had not stated the time of the event "between the two evenings" we would be able
to assume that anytime on the fourteenth would be OK for the slaying of the lamb.  God
made it specific by telling us when on the 14th it must be slain, “between the two
evenings”.  Therefore, the lambs had to be slain in the afternoon of the 14th otherwise we
have contradictions in the scriptures.

It is not wise to base doctrine on the syllables, adverbs, prepositions, and conjunctions of
the Hebrew and Greek languages.  It is a matter of getting too close to the trees to see
the forest.  Occasionally one small word will matter a great deal.  However, if our only
tool is Strong’s Concordance we can hardly find the answer.  Strong used only the
Hebrew root nouns and verbs for his concordance.  

Let us take a closer look at the “waw”.  The word appears in the Old Testament 50,011
times.  Anytime you see the word <and> it is more than likely “waw”.  It is a particle
conjunction and means,
and, so, then, when, now, or, but, that, and has many other meanings
as well.  The “waw” is an inseparable prefix, used as a conjunction or introductory
particle usually translated as "and".  The fundamental use of the “waw” prefix is that of a
simple conjunction "and" connecting words, phrases and complete sentences.  In the
verse under consideration, the “waw” appears twice, once at the beginning of the
sentence and the other in the middle of the sentence.  The KJV translates it both times as

Some early 14th Passover advocates selected the second “waw” in this sentence as a way
to prove that the Passover had to be slain immediately after sunset.  Their reasoning was
that the Israelites were to keep the lambs penned <until> the 14th day.  They then chose
the word <when> as the proper translation asserting that this indicated the lamb was slain
immediately – once the day became the 14th.  Their main problem was that they ignored
the fact that the same verse tells us when on the 14th the slaying took place – “between
the evenings”.  This took the guesswork out of the “waw”.  Furthermore, without
“between the evenings” the future time indicated by the “waw” was merely indefinite
“any time on the 14th day of the first month”.

Exodus 12:6 And ye shall keep it up until the fourteenth day of the same month: and (“waw” – and,
so, then, when, now, or, but, that) the whole assembly of the congregation of Israel shall kill it in the
evening (between the evenings).

Exodus 12:6 And it shall be kept by you till the fourteenth of this month, and all the multitude of the
congregation of the children of Israel shall kill it toward evening.

We have included the “waw” in the heading above.  It is only one consonant of the
Hebrew alphabet and has nearly anyone of the Hebrew vowels attached.  Modern
Hebrew does not use the W sound for this consonant.  They use the V sound instead so the
“waw” become “vav”.  Some question whether the Hebrew Language ever used the W
sound for this consonant.  The “waw” does not stand alone, but prefixes a word.