A.T. Robertson Commentary Romans 4:17

"(as it is written, A father of many nations have I made thee) before him whom he believed, [even] God, who giveth life to the dead, and calleth the things that are not, as though they were." — Romans 4:17 (ASV)

A father of many nations (πατερα πολλων εθνων). Quotation from Ge 17:5. Only true in the sense of spiritual children as already explained, father of believers in God.

Before him whom he believed even God (κατεναντ ου επιστευσεν θεου). Incorporation of antecedent into the relative clause and attraction of the relative ω into ου. See Mr 11:2 for κατεναντ, "right in front of."

Calleth the things that are not as though they were (καλουντος τα μη οντα ως οντα). "Summons the non-existing as existing." Abraham's body was old and decrepit. God rejuvenated him and Sarah (Hebrews 11:19).