Adam Clarke on Ezekiel 16:4

As for thy nativity, etc. - This verse refers to what is ordinarily done for every infant on its birth. The umbilical cord, by which it received all its nourishment while in the womb, being no longer necessary, is cut at a certain distance from the abdomen: on this part a knot is tied, which firmly uniting the sides of the tubes, they coalesce, and incarnate together. The extra part of the cord on the outside of the ligature, being cut off from the circulation by which it was originally fed, soon drops off, and the part where the ligature was is called the navel. In many places, when this was done, the infant was plunged into cold water; in all cases washed, and sometimes with a mixture of salt and water, in order to give a greater firmness to the skin, and constringe the pores. The last process was swathing the body, to support mechanically the tender muscles till they should acquire sufficient strength to support the body. But among savages this latter process is either wholly neglected, or done very slightly: and the less it is done, the better for the infant; as this kind of unnatural compression greatly impedes the circulation of the blood, the pulsation of the heart, and the due inflation of the lungs; respiration, in many cases, being rendered oppressive by the tightness of these bandages.