Exodus 38:26

A bekah for every man, [that is], half a shekel, after the shekel of the sanctuary,.... A half shekel was called a "bekah", from בקע, "bakah", to divide; because it was a shekel divided into two parts:

for everyone that went to be numbered, from twenty years and upwards; in order to give a ransom, and make an atonement for their souls, as was ordered Exodus 30:12

for six hundred thousand and three thousand and five hundred and fifty [men]; so that from the time of their coming out of Egypt, which was now about six months ago, there was an increase of 3550 of the above age; see Exodus 12:37.