כי את הבכר בן השנואה יכיר לתת לו פי שנים (כי תצא כא:יז)

The word “בכר” is written in this passuk without the letter “ו” (it should have been written as follows: “בכור“).  The Arizal writes in his Sefer Hatiyul that the Aleph Beis (Alphabet) contains three letters, each worth double the letter preceding it.  

For example, the numerical value of the letter “ב” is 2 – double that of “א,”whose value is 1. 

Likewise, the value of the letter “כ” is 20, twice that of “י.”

Finally, the letter “ר” amounts to 200 – doubling the “ק,” which has the numerical equivalent of 100. 

These three letters – missing a “ו” – form the word “בכר” – to allude to the fact that the firstborn – the Bechor receives the double portion.