Śatapatha Brāhmaṇa ("of a hundred paths") 4.6.1.6

4.6.1.6

athāsyāṃ hiraṇyam baddham bhavati | tadupajighrati sa yadevātra kṣaṇute vā vi vā liśate 'mṛtamāyurhiraṇyaṃ tadamṛtamāyurātmandhatte

Now there is a piece of gold in that (spoon): that he smells at. And if he either galls or scratches himself at this (sacrifice),--gold being immortal life,--he lays that immortal life into his own self.