דבר אל-בני ישראל ואמרת אלהם ועשו להם ציצת על-כנפי בגדיהם לדרתם ונתנו על-ציצת הכנף פתיל תכלת
Speak to the Children of Israel and tell them: Make for yourselves tzitzis on the corners of your garments, for all generations, and place on the tzitzis of the corners a blue thread
An interesting episode in the Torah is known as the war between the four kings and the five kings. During this battle, Avraham’s cousin Lot is kidnapped. When Avraham rescues him and the king of Amalek, the king offered Avraham all the spoils of war. Avraham strongly refused, not even taking a thread or a shoelace for himself. Rashi explains that his reasoning was he didn’t want to benefit in any way from theft. Our Sages tell us that in reward for this value system, Avraham’s descendants were rewarded with the blue thread of tzitzis and the leather straps of tefillin. At first glance, this is hard to understand. What does a desire to avoid theft have to do with tzitzis and tefillin? Why are these the two mitzvos Avraham was rewarded with?
One can suggest that upon inspection, both of these mitzvos have some connection to theft. With both mitzvos it’s possible to con and deceive people. The blue thread of tzitzis, known as techeiles, is only valid if it comes from a special sea creature known as the chilazon. Due to its rarity, the cost to produce techeiles dye was exorbitant. As a result, con artists were selling a cheap imitation known as kela ilan, commonly translated as the indigo plant, pretending it was techeiles. While the two dyes are indistinguishable, one does not fulfill their mitzvah with kela ilan. We see then that the mitzvah of tzitzis has some connection to stealing.
We find something similar with tefillin. Our Sages tersely tell us that you can’t trust someone wearing tefillin. What does that mean? Con artists were known to wear tefillin so people would trust them. There’s a story with someone who deposited his money with someone wearing tefillin, and when he later came to collect it, the person denied ever receiving money. The depositor lamented that he didn’t know the guy personally to trust him enough, but the tefillin implied he was a G-d fearing Jew. We see that the mitzvah of tefillin also has some connection to theft.
Our Sages teach us that someone who refrains and doesn’t transgress gets reward as if they have fulfilled a mitzvah. If so, when someone properly fulfills these two mitzvos, tzitzis and tefillin, and they don’t con the masses like those that did so in the past, their reward is double. They get rewarded for the mitzvah, and they also get rewarded for not tricking people and stealing from them. It fits perfectly then that Avraham, who was particular about not benefitting in any way from theft, should be rewarded with specifically these two mitzvos.
 Based on Lev Aryeh to Chullin 88b s.v. בשכר שאמר
 Numbers 15:38
 Genesis Chapter 14
 Rashi to Chullin 89a s.v. אם מחוט
 Chullin ad. loc.
 Tosefta Menachos 9:6
 See Maharam to Bava Metziah 61b s.v. תוס’ ד”ה שתולה, who says techeiles is דמיו יקרים בתכלית היוקר
 Aruch § קלא אילן
 Bava Metziah loc. cit.
 Ibid implies only Hashem can tell the difference. In fact, the blue dye produced from the Murex Trunculus (now known as the Hexaplex trunculus), a sea-snail in the Mediterranean Sea, is chemically identical to the dye produced from the indigo plant. Some use this as proof that the Murex Trunculus is the famed chilazon. Although, ironically, some use this exact point as proof that the Murex Trunculus cannot be the chilazon. See Menachos 42b. Some even go so far as to suggest that the Murex Trunculus is kela ilan, seemingly based on the Ben Yehoyada to Bava Metziah loc. cit., although that wouldn’t fit with the Aruch
 Yerushalmi Berachos 2:3, Pesikta Rabbasi § 23, and Midrash HaGadol to Exodus 20:7, brought by Tosafos to Shabbos 49a s.v. כאלישע
 Makkos 3:15
 Cf. Toras Chaim to Chullin loc. cit. for an alternative approach