וַֽיְהִי־עֶ֥רֶב וַֽיְהִי־בֹ֖קֶר י֥וֹם חֲמִישִֽׁי׃ (פ)
Le soir se fit, le matin se fit, — cinquième jour.
Rabbeinu Bahya
A kabbalistic approach: The three years during which consumption of fruit during the first three years is forbidden correspond to the (three highest) emanations, כתר, חכמה, בינה. which are lumped together as one as we have no clear understanding of their workings. This concept corresponds to the period preceding creation of light, a period described in the Torah as tohu vavohu vachoshech, (Genesis 1,2) something which we also cannot fathom exactly with our minds. The fourth year of the tree yielding fruit corresponds to the emanation גבורה, (nowadays known as דין); this corresponds to what the Torah describes as “the spirit of G’d hovering over the expanse of the water,” {Genesis 1,3). This was a period not completely hidden from our ability to comprehend but also not completely revealed, made accessible to our faculties to comprehend. As a result, the Torah demands some form of פדיון, “redemption,” i.e. a process by which that which is beyond our normal capacities is made accessible before we may treat such produce as completely secular, “natural.” The fifth year corresponds to the era commencing with the creation of light, the first part of our material world. As pointed out on earlier occasions the word אור, “light” appears five times in the Torah’s report about its creation. The fifth year of a fruit-bearing tree is compared to the era of world history ushered in with the creation of light. The Torah alludes to this by writing of the fifth year להוסיף לכם תבואתו, with the letter ה added at the end [instead of the letter ו as is the spelling in our versions of the Torah, the pronoun ו “its” referring to the masculine word עץ in verse 23. The author views the letter ה which we do not have and which would be a grammatical inconsistency as an allusion to the five times the word אור, “light,” appears at the beginning of Genesis. Ed.]. In order to remind us of the relationship between the emanations and this legislation the Torah mentions the word ערלה three times in verse 23. In other words, each one of these three first years symbolizes a different concept.