What is the purpose of celebrating a birthday?
Perhaps the answer is found in the verse that speaks about the one-year-old sheep that were brought as sacrifices to the Temple.
“One yearling sheep for a burnt offering” (Numbers 7:75).
In order to qualify as sacrifices, the priests would have to count the 365 days that elapsed from their birth to determine their exact age.
The priests would also evaluate their health, their weight etc.
This is the purpose of a birthday: to look back and count each and every day of the past year, to evaluate where one stands in life.
At times we may find that our ‘sheep’ is completely worthless.
Other times, we may find that our ‘sheep’ is quite valuable.
But the evaluation is obligatory.
When I evaluate my ‘sheep’, I am oftentimes discontented.
Where has my life gone?
Where are all the plans that I had for these seventy-five years?
What did I do with all these years?
I am dissatisfied.
This contemplation reminds me of the Mishna in the Ethics of Our Fathers:
“The day is short, the work is great, the workers are lazy, and the Master of the House presses.” (Chapter 2:20).
–Rabbi Adin Steinsaltz
From a talk on the occasion of Rabbi Adin Steinsaltz's birthday a few years ago.