Keep all documents as evidence that money was a gift from yours relative for at least 7 years.
I have seen cases where Revenue t Canada (CRA now) re-assessed $50.000 from her parent in HK to her son as her unreported income. She didn't keep transfer slip (over 4 years). I told her to request the duplicate from her parent in HK.
Luckily, her parent kept the documents showing the money was to congratulate her being a new mother. I instructed her to tell Appeals Officer that it is a Chinese Tradition for giving Red Packets for such occassion.