Romans 4:19, [Abraham] did not weaken in faith when he considered his own body, which was as good as dead (since he was about a hundred years old), or when he considered the barrenness of Sarah’s womb.
Abraham’s faith overcame reason. Though by reason Abraham knew it was impossible for Sarah to conceive not only because she was about 90-years-old but also because her womb was naturally barren, by faith Abraham believed God and God counted it to him as righteousness (vv. 3-5). His faith in God’s promise overcame his reason. What his reason said how things are naturally supposed to be, his trust in God’s promise reminded him otherwise. Thus, his hope in God did not put him to shame (cf. Romans 5:1-5), and he met God’s promise.
Let us, therefore, not put our trust in our reason but God’s promise. When our reason convinces us we are damned and deserve Hell (for indeed we do), let us rather trust in the external Word of God, which says we were buried with Christ in our Baptism and rise as new creatures in Him (Romans 6:4, 8-11). Which says we have full redemption in His blood—the forgiveness of all our debts according to His abundant grace (Ephesians 1:7). Which says we will be with Christ in Heaven (Revelation 7:13-17; 21:4-8). When our reason gives us cause to doubt, let us put our hope in these promises of God, for He will not put our faith to shame.