The Shulhan Aruch brings the custom to bake the Massot for the Seder Night on Ereb Pesach after Hasot (Midday). While this is certainly a praiseworthy practice, extra precautions must be taken with regard to the "Perurim"-scraps of dough left over from the kneading and rolling of Massa. They will inevitably become Hames, and it is too late to perform "Bitul Hames"-nullification of the Hames, since after Hasot, one is already liable for any Hames in his possession. Therefore, the Shulhan Aruch recommends that before the kneading, all workers stipulate that any leftover dough will be "Hefker"-ownerless, before it becomes Hames.
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The Zohar HaKadosh teaches that one should always spend money to perform Misvot. If one receives his Misvot free of charge, e.g. free Massa, the "Hisonim"-forces of impurity are able to latch on to the Misva. The money paid in exchange for the Misva becomes like a "Pidyon"- scapegoat, drawing the negative forces to it, leaving the Misva unscathed. This is why the Sadikim would refuse to receive their Misva items as a gift. In fact, when the Arizal (Rav Yishak Luria of Safed, 1534-1572) would purchase his Etrog, he would place a large sum of money on the counter to indicate that he was not looking for a bargain and intends to pay for his Misva.
SUMMARY:
When baking Massa on Ereb Pesah, one must stipulate in advance that any leftover dough will be Hefker before it becomes Hames.
One should make a point to spend money when purchasing Misva items, such as Massa.
