A.T. Robertson Commentary Romans 4:19

"And without being weakened in faith he considered his own body now as good as dead (he being about a hundred years old), and the deadness of Sarah`s womb;" — Romans 4:19 (ASV)

Without being weakened in faith (μη ασθενησας τη πιστε). "Not becoming weak in faith." Ingressive first aorist active participle with negative μη.

Now as good as dead (ηδη νενεκρωμενον). Perfect passive participle of νεκροω, "now already dead." B omits ηδη. He was, he knew, too old to become father of a child.

About (που). The addition of που (somewhere, about) "qualifies the exactness of the preceding numeral" (Vaughan). The first promise of a son to Abraham and Sarah came (Genesis 15:3f.) before the birth of Ishmael (86 when Ishmael was born). The second promise came when Abraham was 99 years old (Genesis 17:1), calling himself 100 (Genesis 17:17).