Ta'anis 5a: In the days of Yo'el, there was an awesome famine. The first rain came on Nisan 1. The Navi told them to plant their last seeds; it grew miraculously fast. The ox cried while plowing, and ate fodder in the furrow on the way back; Yisrael were able to offer the Omer on the 16th.

Rashi: So Yisrael sow Tzedakah in front of Hashem, amidst tears, in Galus.

Radak: He cries while seeding, amidst fear lest the seeds not sprout due to the land's dryness. Hashem sees his tears and has mercy on him and sends rain, so at the time of harvest "Bo Yavo v'Rinah."

Malbim (at the end of 5): This depicts one who sowed a dry land, and when he goes to reap he does not know that springs already watered the land, so he is still crying. He thinks that he will reap only as much as he sowed.

Radak: It is the costliness of the seeds, like "u'Meshech Chachmah mi'Peninim" (Iyov 28:18) - the dearness of Chachmah. Something expensive is called Meshech, for its name is Nimshach (extends) a long way. Seeds are expensive in a dry land. This is a parable for Yisrael in Galus. They bear a heavy burden of taxes in order to fulfill Torah and Mitzvos (seeds).

Malbim: It is the amount that he sowed (refer to 126:6:1:4).

Rashi: It is in the future, when Hashem will pay to them their reward.

Radak: It is the time of Ge'ulah, when the exiles will come to Eretz Yisrael

Malbim: It is sudden Simchah (the sheaves grew miraculously fast).

Refer to 126:6:1:1, 3.

Radak: This is the good that Hashem will do to the exiles when they return; they will leave Galus with silver and gold.

Malbim: It is success. They expected a small salvation, like in the days of Koresh (they returned to Eretz Yisrael under the authority of Melech Peras), and they found a great salvation.