Midrash su Amos 8:5

(Fol. 90b) Our Rabbis were taught: Those who store up fruit for speculation, usurers, fraudulent measurers and food speculators, concerning them, the passage reads (Amos 8, 5) When will the new moon be gone, that we may sell provisions? and that we open the corn warehouses, making the epha (measure) small and increasing the shekel, and cheating with deceitful balances. What is written immediately after this? Sworn hath the Lord by the Excellency of Jacob, surely I will not forfeit to eternity all their deeds. Who are meant by those who store fruit for speculation? R. Jochanan said: "People like Sabbati. The father of Samuel used to buy grain at harvest-time, and sold it at the same price. Samuel, his son, however, used to store up the grain he bought in harvest until the price became higher, and then sold it at the same price as in harvest time." And from Palestine the following message was sent: "The acts of the father are more esteemed than those of his son." Why so? Because when the market becomes low (prices fall) it remains so [for the rest of the year, and this was the ease of Samuel's father].