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 (eqb) , "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 30:12-15 )

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 ) .