וְשֵׁ֥שׁ שָׁנִ֖ים תִּזְרַ֣ע אֶת־אַרְצֶ֑ךָ וְאָסַפְתָּ֖ אֶת־תְּבוּאָתָֽהּ׃
And six years thou shalt sow thy land, and gather in the increase thereof;
Rashi on Exodus
ואספת את תבואתה AND SHALT GATHER IN THE INCREASE THEREOF — אסף is a term denoting “bringing into the house”, like, (Deuteronomy 22:2) “thou shalt gather it (ואספתו) into thine house” (cf. Rashi on Genesis 49:29).
Or HaChaim on Exodus
ושש שנים תזרע את ארצך, and for six years you will seed your land, etc. This commandment is connected to the previous one warning us how to avoid the taste of being an alien, i.e. an exiled person similar to what is written in Leviticus 26,34: "then the land will make up for its sabbaths, etc."
Rashbam on Exodus
ואספת את תבואתה. Into your house, and you need not abandon it to all and sundry except in the seventh year of the cycle, the Sh’mittah year. In that year you must leave it untouched, neither sowing your field nor harvesting it.