John Calvin Commentary Deuteronomy 14:24

"And if the way be too long for thee, so that thou art not able to carry it, because the place is too far from thee, which Jehovah thy God shall choose, to set his name there, when Jehovah thy God shall bless thee;" — Deuteronomy 14:24 (ASV)

And if the way be too long. I am kept from understanding this restriction as referring to the tithes, by the ordinance made elsewhere that whoever would redeem them by a money-payment (Leviticus 27:31), should add a fifth part, and this is omitted here; and again, by the explanation added soon after, that they should bring money with them instead of their offerings, and buy with it oxen and sheep, wine, and strong drink, as they pleased.

In summary, if it was too burdensome for them to bring victims and other gifts from their distant homes, they were permitted to buy at Jerusalem whatever they chose to offer, provided they made no offerings elsewhere.