Parashas Naso
וְכׇל־תְּרוּמָ֞ה לְכׇל־קׇדְשֵׁ֧י בְנֵי־יִשְׂרָאֵ֛ל אֲשֶׁר־יַקְרִ֥יבוּ לַכֹּהֵ֖ן ל֥וֹ יִהְיֶֽה׃
So, too, any gift among the sacred donations that the Israelites offer shall be the priest’s.
Torah Temimah points to R’ Akiva — TT (verified).
וכל תרומה — תניא, ר׳ עקיבא אומר: בא הכתוב ללמדך שאם בא אדם לעשות כל גרנו תרומה רשאי.
English: “And every heave-offering” — it was taught: R’ Akiva says: Scripture comes to teach that if a person wishes to make his entire threshing-floor terumah, he is permitted.
Custom
Chazal permit a person to declare his entire crop as terumah if he so chooses.