Rashi: When You want to bestow good, You oversee the land and water it ¹ .

Malbim: There was famine for three years, and then You watered the land with rain of Brachah.

Radak: You already gave to it rain. This is like "v'El Ishech Teshukasech" (Bereishis 3:16), an expression of desire. You decreed to withhold water until it greatly desired and then You gave it amidst Chesed. So, we in Galus are like an arid land that thirsts for rain of salvation. The prefix Vov means that this already was, or after this happened. The same applies to "Hen Atah Katzafta va'Necheta" (Yeshayah 64:4); we already sinned, and after we sinned, You became angry after we sinned). The same applies to "va'Yibak'u ha'Mayim" (Shemos 14:21).

Rashi: You greatly richen it from Your stream full of water, and thereby prepare for it the grain of people [even] at the ends of the world. Radak - it is as if it says Tasirenah. Likewise, "va'Yadbeku" (Shmuel I, 14:22) and "va'Yadrechu" (Yirmeyah 9:2) are like va'Yadbiku and va'Yadrichu.

Malbim: Via giving rain, You made it very rich, for then it makes grain for its residents.

Radak: After You satiate the land, great streams of water remain from the rain for man and animals to drink. It mentions Elokim, for this is a great, wondrous matter which comes from Him. This is like "Ir Gedolah lEi'lokim" (Yonah 3:3), "k'Harerei Kel" (above, 36:7).

Radak: After You satiate the land and it sprouts, You prepare the land with good winds to make vegetation sprout and prosper; i.e. You save it from Shidafon (parched by the east-wind) and Yerakon (dried and turned straw-yellow). If the land was satiated with rain and vegetation sprouted, but then it was stricken with Shidafon and Yerakon, what does the rain help?