Śatapatha Brāhmaṇa ("of a hundred paths") 3.3.3.5

3.3.3.5

atha yatpañca kṛtvaḥ paṇate | saṃvatsarasammito vai yajñaḥ pañca vā ṛtavaḥ saṃvatsarasya tam pañcabhirāpnoti tasmātpañca kṛtvaḥ paṇate

And as to his bargaining five times:--the sacrifice being of equal measure with the year, and there being five seasons in the year, he thus obtains it (the sacrifice, Soma) in five (divisions), and therefore he bargains five times.