ויש סוד גדול בדבר שלא יאבד זמן מן הזמנים לישב בטל, כי כל זמן וזמן הוא ענין בפני עצמו בסוד התפשטות ענף מענפי שם ידו”ד, ועל זה בא הרמז בפרשת וארא ‘אני ידו”ד,’ ופירש רש”י, ‘אני ידו”ד — נאמן לשלם שכר,’ כי זמן זמנים זמניהם כולם סובבים על שם ידו”ד בשרשו ובהתפשטות ענפיו. -של”ה, פרשת ויצא
The ShLa”H here refers to the kabbalistic concept that every moment of time comes into existence through a change in the interface between HaShem’s Four-Letter Name and the created world. This name brings the world into existence, and, the kabbalists explain, in order for any change to occur in the world, something must change, so to speak, in the name of HaShem. So the letters (and vowels) of the name continually change combination in the supernal realm (according to a pattern) which allows for the phenomenon of time and thereby, change within the world, to take place.
Therefore, petitions the ShLa”H, it is incumbent upon every person to utilize every moment to its fullest, for every one is unique and will never come again and eac h represe”nts a unique opportunity to connect to HaShem, fomenting a “tikun” that can never be duplicated at any other time.
It is for this reason that Rashi explains HaShem’s statement, “I am HaShem (Four-Letter Ineffable Name),” to mean, “the One who is faithful to pay reward, for every moment, with its unique quality, carries a unique reward. Not a single moment goes by that HaShem does not reckon for its unique reward to each individual who fulfilled the unique potential of that moment as brought into existence by His Name, or, Heaven forfend, the heavy consequence borne by one who allows that moment to pass unfulfilled.