Final answer:
In the original 1960 version of "Shop Around" by Smokey Robinson and The Miracles, the last line as the song fades is "I know you can, my son," and there are no additional lines after this phrase.
Step-by-step explanation:
The last line that is said in the original 1960 version of "Shop Around" by Smokey Robinson and The Miracles, after the mother's advice to her son about being a man and finding a good wife fades out, is indeed "I know you can, my son." This version does not contain any additional lines after this phrase. Different versions or recordings of the song might have slight variations, but the version in question closes with that line.