16 Do not err, my beloved brethren.
17 Every good gift and every perfect gift is from above, and cometh down from the Father of lights, with whom is no variableness, neither shadow of turning.
THIS scripture is to remind us of WHERE our good gifts and blessings come from.
One of the ATTRIBUTES of GOD is that HE IS GOOD.
GOODNESS is an attribute of GOD. HE is ALWAYS GOOD. Consequently, HIS GIFTS and Blessings HE bestows upon HIS children ARE ALWAYS GOOD.