Śatapatha Brāhmaṇa ("of a hundred paths") 3.1.3.17

3.1.3.17

tadyatpañca kṛtva ānakti | saṃvatsarasammito vai yajñaḥ pañca vā ṛtavaḥ saṃvatsarasya tam pañcabhirāpnoti tasmātpañca kṛtva ānakti

And the reason why he anoints five times, is that the sacrifice is of equal measure with the year, and five seasons there are in the year: he thus obtains possession of the latter in five (divisions), and therefore he anoints five times.