In the third month they began to lay the foundations of the heaps, and in the seventh month, they finished them.

in the third month they have begun to lay the foundation of the heaps, and in the seventh month they have finished.

The first store of things was put down in the third month, and in the seventh month the masses were complete.

In the third month, they began to lay out the foundations of the stacks. And in the seventh month, they finished them.

The third month - Compare 2-Chronicles 29:3; 2-Chronicles 30:2, 2-Chronicles 30:13. The events hitherto described - the destruction of the high places, the re-appointment of the courses, and the re-establishment of the tithes followed so closely upon the Passover, that a month had not elapsed from the conclusion of the Feast before the gifts began to pour in. In the seventh month the harvest was completed; and the last tithes and first-fruits of the year would naturally come in then.

In the third month - "The month Sivan; the seventh, Tisri." - Targum.
The heaps - The vast collections of grain which they had from the tithes over and above their own consumption; see 2-Chronicles 31:10.

In the third month they began to lay the foundation of the heaps..... The month Sivan, as the Targum, in which month was the feast of Pentecost, called the feast of the harvest, Exodus 23:16, for then barley harvest was ended, and wheat harvest began, and the firstfruits were brought:
and finished them in the seventh month; the month Tisri, as the Targum, in which was the feast of tabernacles, sometimes called the feast of ingathering, of the fruits of the earth, the wine, oil, &c. and so a proper time for bringing the tithes of all.

In the third month, consequently immediately at the end of the grain harvest, they commenced to found the heaps (to lay the foundation of the heaps); and in the seventh month, i.e., at the end of the fruit and wine harvest, they completed them (the heaps). In the third month fell pentecost, or the harvest feast; in the seventh, the feast of tabernacles, after the gathering in of all the fruits. ליסּוד has Daghesh in ס, because this verb in the imperf. assimilates its י like נ to the second radical, and the infinitive is formed after the imperf.; cf. Ew. 245, a.

Third month - Of the sacred year, in which their harvest began. Seventh - In which their harvest ended and the feast of tabernacles was kept.