In Galatians 3, Paul tells us that the promises to Abraham include a reference to 'offspring' (singular) rather than 'offsprings' (plural) or descendants.
16Now the promises were made to Abraham and to his offspring. It does not say, “And to offsprings,” referring to many, but referring to one, “And to your offspring,” who is Christ. ESV
However the promises as recorded in Genesis don't seem to back that up, such as this from chapter 22:
15And the angel of the Lord called to Abraham a second time from heaven 16and said, “By myself I have sworn, declares the Lord, because you have done this and have not withheld your son, your only son, 17I will surely bless you, and I will surely multiply your offspring as the stars of heaven and as the sand that is on the seashore. And your offspring shall possess the gate of his enemies, 18and in your offspring shall all the nations of the earth be blessed, because you have obeyed my voice.” ESV
Is Paul misquoting Genesis or re-interpreting it or something else?