Where in tanach is the mitzvah of Netilat Yadaim shown / present?
I am essentially asking for the source of the mitzvah.
רבא אמר מצוה לשמוע דברי ר"א בן ערך דכתיב וכל אשר יגע בו הזב וידיו לא שטף במים אמר ר"א בן ערך מכאן סמכו חכמים לנטילת ידים מן התורה
Rava says: It is a mitzva to listen to the statement of Rabbi Elazar ben Arakh, as it is written with regard to a man who experiences a gonorrhea-like discharge [zav]: “And whomever he that has the issue touches, without having rinsed his hands in water,” he contracts ritual impurity (Leviticus 15:11), and Rabbi Elazar ben Arakh says: From here the Sages based washing of the hands upon a verse from the Torah.
See Berachos 53b
אָמַר רַב נַחְמָן בַּר יִצְחָק: אֲנָא לָא זִילַאי וְלָא זִיוַאי וְלָא זוּהֲמַאי יָדַעְנָא אֶלָּא מַתְנִיתָא יָדַעְנָא. דְּאָמַר רַב יְהוּדָה אָמַר רַב וְאָמְרִי לַהּ בְּמַתְנִיתָא תָּנָא: ״וְהִתְקַדִּשְׁתֶּם״ אֵלּוּ מַיִם רִאשׁוֹנִים, ״וִהְיִיתֶם קְדֹשִׁים״ אֵלּוּ מַיִם אַחֲרוֹנִים, ״כִּי קָדוֹשׁ״ — זֶה שֶׁמֶן, ״אֲנִי ה׳ אֱלֹהֵיכֶם״ — זוֹ בְּרָכָה. Rav Naḥman bar Yitzḥak said of this: I do not know of Zilai or Zivai or Zuhamai; rather, I know a baraita, as Rav Yehuda said that Rav said, and some say that it was taught in a baraita: It is stated: “And you shall sanctify yourselves, and you shall be holy, for holy am I, the Lord your God” (Leviticus 20:26). With regard to this verse, the Sages said: And you shall sanctify yourselves, these are the first waters with which one washes his hands before the meal; and you shall be holy, these are the final waters; for holy, this is oil which one spreads on his hands; am I, the Lord your God, this is the Grace after Meals blessing.
(Exodus 30:19): “And Aaron and his sons shall wash their hands and their feet . . . when they come near to the altar to minister.”
This is the direct commandment in the Torah for handwashing, but do know that this applies specifically to Kohanim and to temple service.
However we want all of the Jewish people, specifically the Kohanim to be pure, and so all Jews wash their hands before bread.
Also you can see in Tehillim 26:6
ואֶרְחַ֣ץ בְּנִקָּי֣וֹן כַּפָּ֑י וַֽאֲסֹֽבְבָ֖ה אֶת־מִזְבַּֽחֲךָ֣ יְהֹוָֽה: 6 I washed my hands with cleanliness, and I encompassed Your altar, O Lord.
There are tons of references and examples of hand washing in my humble opinion in Tanach. Interestingly Avraham washes the Angels feet who visit him due. Though this is different (the Kohanim though wash both hands and feet) you can see that there are many references depending how specific or vague you are interested in being.