Blue Cord

Numbers 15:39
You will have these tassels to look at and so you will remember all the commands of the LORD , that you may obey them and not prostitute yourselves by going after the lusts of your own hearts and eyes.

I had a vague idea of these tassels looking something like the ones for sale in the fabric store to decorate pillows and curtains. So I decided to check into it.
The full description is a tassel on the corners, with a blue cord. The commentary I found, in bibletopics.com, says that hems were fringed. At the corners, those fringe threads were gathered into tassels with the blue cord.
The blue cord was important because the blue dye--a violet-blue--was bought from traders, and not easily produced as it came from snails. Blue stands for heaven. The rest of the garment was undyed linen. The single wool cord, heavenly blue, was a visual aid, a continual, silent call to worship.
Here the heart is very human, very fallen, the source of lusts. Yet we can master our wayward hearts. With our minds we learn to remind ourselves of God's commands, so essential to our lives and happiness, when we look on something we've taught ourselves to use as a reminder: a simple bit of heaven-blue yarn.