Database
[{"_id":ObjectId("6026ed7f44f27b89024a9604"),"sig_nam":"xyz","cont_name":"1","comment":[{"pRating":5,"_id":ObjectId("6026ed7f44f27b89024a9603"),"replies":["cm1","cm2"]},{"pRating":6,"_id":ObjectId("6026ed7f44f27b89024a9607"),"replies":["1_cm1","1_cm2"]}]}]
Query
db.collection.update({"comment":{$elemMatch:{_id:ObjectId("6026ed7f44f27b89024a9603")}}},{$push:{"comment.$.replies":"yaser"}})