Bamidbar 15:37-41
וַיֹּאמֶר יְהוָה אֶל מֹשֶׁה לֵּאמֹר. דַּבֵּר אֶל בְּנֵי יִשְׂרָאֵל, וְאָמַרְתָּ אֲלֵהֶם, וְעָשׂוּ לָהֶם צִיצִת עַל כַּנְפֵי בִגְדֵיהֶם לְדֹרֹתָם; וְנָתְנוּ עַל צִיצִת הַכָּנָף — פְּתִיל תְּכֵלֶת. וְהָיָה לָכֶם לְצִיצִת, וּרְאִיתֶם אֹתוֹ וּזְכַרְתֶּם אֶת כָּל מִצְוֺת יְהוָה וַעֲשִׂיתֶם אֹתָם; וְלֹא תָתוּרוּ אַחֲרֵי לְבַבְכֶם וְאַחֲרֵי עֵינֵיכֶם, אֲשֶׁר אַתֶּם זֹנִים אַחֲרֵיהֶם. לְמַעַן תִּזְכְּרוּ וַעֲשִׂיתֶם אֶת כָּל מִצְוֺתָי; וִהְיִיתֶם קְדֹשִׁים לֵאלֹהֵיכֶם. אֲנִי יְהוָה אֱלֹהֵיכֶם אֲשֶׁר הוֹצֵאתִי אֶתְכֶם מֵאֶרֶץ מִצְרַיִם, לִהְיוֹת לָכֶם לֵאלֹהִים, אֲנִי יְהוָה אֱלֹהֵיכֶם.
And YHWH spoke to Moshe, saying: Speak to the children of Israel, and you will recite to them, that they shall make for themselves hanging strings (Tzitzith) on the corners of their Begged for their generations; and they shall place on the hangings strings of the corner, a thread of Ticheilleth. And it shall be to you all for hanging strings, and when you all will see it (him), and you all will remember all the commandments of YHWH, and you all will do them; and you all will not follow after your hearts, and and after your eyes, which you all stray after them. So that you all will remember and you all will do all My commandments, and you all will be set aside for your God. I am YHWH your God, that I brought you all out of the land of Egypt, to be to you all as your God. I am YHWH your God.
Devarim 22:12
גְּדִלִים תַּעֲשֶׂה לָּךְ, עַל אַרְבַּע כַּנְפוֹת כְּסוּתְךָ, אֲשֶׁר תְּכַסֶּה בָּהּ.
Cords you shall make on the four corners of your covering, with which you cover with.
Mishna - Mennachoth 3:9-4:1
אַרְבַּע צִיצָיוֹת מְעַכְּבוֹת זוֹ אֶת זוֹ — שֶׁבְּאַרְבַּעְתָּן מִצְוָה אַחַת. רְבִּי יִשְׁמָעֵאל אוֹמֵר: אַרְבַּעְתָּן אַרְבַּע מִצְווֹת. הַתְּכֵלֶת אֵינָה מְעַכֶּבֶת אֶת הַלָּבָן, וְהַלָּבָן אֵינוּ מְעַכֵּב אֶת הַתְּכֵלֶת.
[Damage that causes the absence of any of the] four [sets of] hanging strings [on four corners] invalidate the others, as the four of them are a single commandment, R Yishmael says: the four of them are four commandments. The Ticheilleth doesn't invalidate the white, and the white doesn't invalidate the Ticheilleth.