Shatapatha Brahmana 4.6.1.8

4.6.1.8

athāsyāṃ hiraṇyam baddam 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.