It's one of Judaism's most important commandments for a Jew because it encompasses everything a Jew needs to do.
A Jew who strives to be holy will also be ethical, loving, kind, compassionate, wise, keep Shabbat, keep kosher, avoid lashon hara, and much more.
And being holy starts on the inside.
Because Hashem is Holy.
Just like people imitate the superficial fashions of royalty, we should strive to imitate the Holiness of our King: Hashem.
That is the path to fulfilling our soul's purpose in life.
So what's an important step in achieving this?
Look at what the Torah says about Hashem.
On pages 6-7, Rav Miller discusses the anthropomorphic descriptions of Hashem: a strong arm, flaring nostrils, jealous or angry or happy feelings, and so on.
He explains the Rambam's view of it and other views, and why the anthropometrism is so meaningful (despite its lack of accuracy—Hashem isn't physical).
Let's say you want to be a public speaker.
So one of the great teachers of public speaking once wrote a book and he said that if you want your audience to fall asleep on you so speak in abstractions.
Abstract ideas are difficult to keep your mind on it and after a while your attention wanders and you fall asleep.
Talk about abstract ideas, concepts that are far from the mind, and they’ll be sleeping in no time.
You want people to listen to you? Speak about things that are actual objects.
Speak especially about people.
Do that and you’ll get their interest because people are interested in people.
They can picture people because it's like themselves.
How to Emulate Hashem's Love
Hashem is the biggest Ohev Yisrael possible.
He loves you much more than any human being loves you or ever could love you.
So if Hashem loves Jews (and Hashem loves everybody, but especially the people He chose who chose Him too), then we need to work on loving Jews too—with particular emphasis on those who actually follow the Torah (or at least try to).
Jews who keep Torah are the ones who still choose Hashem. With all our imperfections, at least we do not reject Hashem.
We should actively seek out the positives in different frum communities and also each other.
Even if someone misses the mark, we can still appreciate their intentions.
For example, a lot of frum women who dress immodestly feel like they davka make a kiddush Hashem by dressing so fashionably.
That's their sincere intention.
Others claim to do it for their husband, yearning to always find favor in his eyes & be a good, pleasing wife.
They are wrong to sink to immodesty on both accounts. Yet their intentions are good. And you can still see them as basically good (albeit misguided) based purely on their intentions.
(Side note: And if you do discover an opportunity to enlighten them about genuine kiddush Hashem or pleasing their husband without transgressing the Torah, approaching them with feelings of love & appreciation in your heart increases the likelihood of acceptance because you see them as good, wonderful women—and you don't relate to them with a totally lack of sympathy, as if you wholly despise or condemn them, as if you have no flaws to work on within your own self.)
2 Baby Steps toward Fulfilling "Kedoshim Tihiyu"
He uses the example of a regular woman on the phone who has been chitchatting (i.e., for social enjoyment, not essential issues) for a long time.
A short to medium chat can be a nice mental respite that re-energizes a person.
But now it has been a very long chat.
So she thinks to herself (page 8), “Maybe I shouldn't talk so much on the telephone. I should fulfill the mitzvah of kedoshim tihiyu now and hang up the phone.”
Part of being kadosh is not showing off or making her friend feel unworthy. So she shouldn't announce her holy intention, but make some other excuse.
Another idea can be utilized at a Shabbat meal when everyone feels the need to offer their opinion.
Rav Miller suggests thinking: “Kedoshim tihiyu! Hashem doesn’t open His mouth to speak unless it’s needed so I’m going to be like Him.”
Look, if something really needs to said, you can say it.
But a lot of times, it's not absolutely necessary.
Rav Miller acknowledges that maybe you cannot restrain yourself for the entire meal.
But even 5 minutes is an accomplishment!
Those 5 minutes already start training you and reinforcing a good habit.
As Rav Levi Yitzchak Bender once said:
For every Jew contains within a precious gem, only that gem is covered and invisible.
And through a little bit of self-sacrifice—sleep a little less, eat with a bit less taavah and the rest of the matters of kedushah—that precious gem is revealed.
(When all sorts of talmidei chachamim from different groups, cultures, and eras all say the same thing, then you know you're dealing with an authentic, fundamentally Torah view.)
More Practical Suggestions
On page 10, he also explains the great value of the book Tomer Devorah:
...it’s worth making the time to study the Tomer Devorah even if it’s just to get a glimpse of the greatness that is expected from the Jewish people.
The words of that little sefer have already entered the bloodstream of the Jewish people – you may not be aware of it, but these middos, the way they have been explained in the Tomer Devorah, have become our national possession and the ideal to which we strive.
Basically, every time we use our abilities for something not in the spirit of Torah, it's the same as a person who receives a monetary stipend, and who then uses that money to buy stamps & stationery to send insulting letters to his benefactor!
Yet his benefactor continues to supply him with the means to buy stationery.
Hashem relates to us with this same humility and forbearance.
Likewise, says Rav Miller (gleaning from Tomer Devorah), we too should relate to others with humility & patience.
(There are exceptions when you should not be so nice to a bad person—or times you should even fight fire with fire. But in general, keeping score and responding to a negative behavior with your own negative behavior or even revenge...this reduces your holiness.)
On pages 12-13, Rav Miller describes one example of how to do this in marriage.
On page 13, he offers examples of how to do this in business situations.
On page 14, he states suggestions for doing this in marriage (a different suggestion from the one above) and in social situations.
A significant component of this is your intention.
Sure, you can do all the above for the sake of peaceful relations with others.
And that's a very positive reason.
But Rav Miller recommends taking it one step further and thinking to yourself that you wish to fulfill the above for the sake of fulfilling the command: "kedoshim tihiyu."
For yet another doable tip, please check out the Practical Tip on page 15.
Bringing Forth Your Inner Gold
When you practice what we spoke about tonight you’re going to cause your latent abilities, the hidden middos which reflect all the ways of Hashem, to come to the surface.
By means of modeling your behavior and your thoughts and your actions after His, then kedoshim tihiyu – you’re going to become more and more perfect all the time because it will bring forth from the recesses of your soul all of the golden qualities that you have within you.