The reason a wife would traditionally stand to the left of her husband is because a man’s right arm was considered his sword arm. Should a husband have to protect his wife, he would hold her in his left arm and fight off any danger with his right arm. It was therefore in the wife’s best interests to always stand on the left of her husband.
Even Lord Shiva, gave his left half to Shakthi, Arthanaareeshwarar is also depicted like that. It is in the Arthanareeswara sankalpam. Wife is considered Ardhangini; Wife is the VAMANGI. I.e. the left half of the GRIHASTHA. The left side of the husband indicates the Chandra nadi (Moon channel).
All religious rituals and fasts are commenced by women. … Whenever a husband and wife were introduced the woman’s name would precede the man’s in any religious ritual the resolve (sankalpa) this is followed in all rituals. Heart is on the left side of the body, and wife is the heart of her husband. So many things has this inner meaning, before tying the mangal sutra the woman was made to sit to bridegrooms right and after that she will be in his left always. 
A wife sits on her husband’s left side at the time of donating vermilion (Sindoor) making a re-entry after marriage or ‘gona’ taking meals, and while serving at the time of seeking blessings, wearing clothes, rinsing feet of the Brahmins.
At the time of marriage of her daughter, installation, sacrificial, and other religious rites the wife should sit on right side of her husband. Similarly, the wife and the son should remain on the right side at the time of performing ceremony on the birth and at Naam of the child, while consuming food and making an exit.
This articles answer following question:
When blessing someone, as per Hindu tradition, why should a wife always stand to the right of the husband?
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