The combination of wool and linen in a garment is called Sha'atnez and is prohibited by the Torah (Lev. 19:19, Deut. 22:11).
Though tradition regards this as a statute, a Divine ordinance which is a test of human obedience, Nachmanides points out that it comes in a context of the intermixing of various species, seeds and animals, and may indicate that the Creator has established boundaries between categories within the created world and man must respect the structure ordained from above.
The Tower of Babel is an object lesson: one humanity speaking one language is a noble idea, but God ordains that nations shall be separate and languages shall be different.
Some will argue that this flies in the face of endeavours to unite humanity; the Torah answer is not to reject unity but to argue for unity within diversity. We do not have to be the clones of each other; we have to be ourselves and love and respect the other, differences and all.
TELL HIM OFF – BUT NOT ALWAYS
If someone is doing the wrong thing, you have to rebuke him (Lev.19:17). It is like the duty you have to save a person from danger. If you can see that they are stepping into obvious risk, you cannot stand idly by.
The same applies to a person who is breaking a law of the Torah: if you refrain from speaking out, you have a share in the responsibility for the risk they are taking with their eternal life. It is not only their wellbeing which you are protecting, but your own. If you ignore actual or possible evil around you, you show yourself as a hard-hearted, irresponsible citizen.
What about a situation in which no-one is going to take any notice of your warning or rebuke? For the sake of your own conscience you cannot remain unmoved, but you might make a laughing stock of yourself. Hence the sages say, “Just as it is a duty to say that which will be heeded, so it is a duty not to say that which will not be heeded” (Talmud Yevamot 65b).
HOLINESS & HELPFULNESS
Ask what the Torah’s definition is of holiness in the 19th chapter of Vayikra and you will find that being holy is being helpful. That chapter doesn't contain too much about prayers or piety, tabernacles or temples, sacrifices or Scriptures, meditations or mystical raptures, but a great deal about the ordinary dimensions of daily living – how to relate to one another, how to build a family and community, how to handle the people who live in your street, how to speak with the shopkeepers and street-sweepers, how to plan the working week.
Chief Rabbi JH Hertz on that 19th chapter writes: “Holiness is not so much an abstract or a mystic idea, as a regulative principle in the everyday lives of men and women.
“The words, ‘You shall be holy’, are the keynote of the whole chapter, and must be read in connection with its various precepts; reverence for parents, consideration for the needy, prompt wages for reasonable hours, honorable dealing, no tale-bearing or malice, love of one’s neighbor and cordiality to the alien, equal justice to rich and poor, just measures and balances – together with abhorrence of everything unclean, irrational, or heathen.
“Holiness is attained not by flight from the world, nor by monk-like renunciation of human relationships of family or station, but by the spirit in which we fulfil the obligations of life in its simplest and commonest details: in this way – by doing justly, loving mercy, and walking humbly with our God – is everyday life transfigured.”
This is the sense in which Jerusalem is a holy city.
Go shopping in Jerusalem, and the checkout clerk will tell you there’s a special on this week and you don’t need to spend so much.
When you tell a taxi driver your destination, he’ll tell you it’s better to take a different route.
When you sit opposite an English speaker in the bus, you may end up inviting them home for a meal.
When you drop coins in a mendicant’s collecting tin, they’ll wish you a good year.
When you encounter an ex-Russian engineer singing in the street to make a living, you not only put some coins in their violin case or collecting tin but you sing along with them. When anyone is in trouble in Jerusalem, everyone wants to help.