Quomodo si - Isaiah 66:13

Quomodo si cui mater blandiatur, ita ego consolabor vos. As one whom the mother caresses, so will I comfort you.

What is si doing in this sentence? I’m assuming that it’s to be taken in conjunction with quomodo, but I couldn’t examples of that construction in Lewis and Short.

si + quis (cui) = “if anyone” = “anyone who”