Then Mary took about a pint of pure nard, an expensive perfume; she poured it on Jesus' feet and wiped his feet with her hair. And the house was filled with the fragrance of the perfume.

Mary of Bethany is one of Lzarus' two sisters (the other one being Martha). In the Bible, one important event is the anointing of Jesus. Mary is said to have poured perfume (nard) over the head and/or feet of Jesus, and to have wiped it with her her and/or clothes.

I'm sorry I don't have a very good source other than the Bible itself, namely John 12:3. I remembered the anointing of the feet from my childhood stories and quickly looked for the part of the book that covers it.

Edit: on a related and perhaps more interesting/in depth question, I notice there is indeed a lot of feet-washing involved in the Scripture. Is this a biblical thing only? Was the bathing and purification of one's feet a widespread ritual in Judea/Mesopotamia/the "wide middle East" in ancient times?

If you are asking about what the widely accepted readings of this icon are, as opposed to questions that might require an academic expert in the history of Eastern Orthodox icons, you might get some very good answers on r/OrthodoxChristianity. You also might get some answers that are at an academic level there too, since it's quite likely something some participants in that subreddit have studied at an academic level.