The six letters beth gamal dalath kaph pe and taw are the hinge of Syriac pronunciation. Each writes a stop in some positions and the matching fricative in others, so one letter covers two sounds and the reader has to know which is called for. The rule that governs the choice belongs to the grammar of the word, not to the letter, and a reader who knows Syriac applies it without thinking about it.
Beth is the first of the six and the easiest case to hear, since the difference between a b and the fricative that answers to it is wide. The pointing that can settle the matter, a dot above for the plosive and a dot below for the fricative, was developed for teaching, for scripture and for careful copies rather than for everyday writing, and most Syriac on most pages carries neither mark.
That has a consequence for anyone reading a manuscript rather than a modern edition. Two words spelled with the same letters may differ only in whether a beth is hard or soft, and nothing on the page decides it. Editors add the points, and in doing so make a reading rather than merely transcribing one. The practice is old and is not a modern imposition, but it is still an act of interpretation, and a careful edition says which points are in the manuscript and which are the editor.
Beth is also the Syriac preposition b, meaning in or with, prefixed directly to the word it governs, so a reader meets the letter at the head of a word constantly.