“For while we were still weak, at the right time Christ died for the ungodly.” -Romans 5:6
Here Paul begins a new argument founded on the previous assertion regarding the love of God being poured out to us. He will argue from the greater to the lessor. That is, he will show that if God is willing to die for the ungodly (greater sinners), how much more will he keep those whom he has made righteous (lessor sinners).
But let us focus on this part of the argument, today. He says, while we were still weak. (Gr. Asthenes = weak) means helpless in a moral sense. Recall Paul’s earlier explanation: “Now we know that whatever the law says it speaks to those who are under the law, so that every mouth may be stopped, and the whole world may be held accountable to God. For by works of the law no human being will be justified in his sight, since through the law comes knowledge of sin.” -Romans 3:19–20
And in 5:6, the context further reveals this fact in that weak corresponds with ungodly. While we were weak (morally destitute), Christ died for the ungodly (Gr. Asebes), those who violate norms for a proper relation to deity, the impious.
But what is meant by at the right time? Paul explains this more fully in his letter to the Galatians.
“But when the fullness of time had come, God sent forth his Son, born of woman, born under the law, to redeem those who were under the law, so that we might receive adoption as sons. And because you are sons, God has sent the Spirit of his Son into our hearts, crying, “Abba! Father!”” -Galatians 4:4–6
What Paul is demonstrating is that salvation is the master-plan of God, orchestrated in history by him for us, and each aspect has unfolded at it’s appropriate time. And at the writing of his letter to the Romans, the right time for the incarnation, death, burial, resurrection, and ascension of the Christ had come upon them, in the person of Jesus.