The connection seems to be this: “You, like them, have promises — promises to which God has given all possible certainty; you, like them, can attain the fulfilment only through faith and patient waiting.”
For when God made promise. — It is better to follow the words literally, For when to Abraham God had made promise. Abraham is chosen for special mention as the most illustrious example of those who “inherit the promises” (comp. John 8:58); also because (1) the assurance given to him was confirmed by oath; and (2) in it lay included the promise of the Christ. The promises made to Abraham were essentially one, with various parts progressively fulfilled. It seems likely that, though the next verse is quoted from Genesis 22:17, the writer also has in mind (“had promised”) Genesis 12:3, and especially Genesis 15.