20. "But how can I be sure that my faith is strong enough to save my soul?”

It is not faith that saves the soul. It is the One whom God has set forth as the object of faith. It is true we are justified by faith instrumentally, but actually we are justified by His blood. The weakest faith in Jesus saves. The strongest faith in self, or in good works, or in the church, or in its ordinances leaves you lost and undone still.
James Parker of Plainfield, N. J., was visiting in a hospital, when a nurse indicated a bed surrounded with white screens, and whispered, "The poor man is dying. The priest has been here and administered the last sacrament. He cannot live long." Mr. Parker begged to go inside the screen, and permission was granted. As he looked down upon the dying man he observed a crucifix on his bosom. He stooped over and lifted it up. The sick man lifted his eyes and looked distressed. "Put it back," he whispered, "I want to die with it on my breast." The visitor pointed to the figure pictured on the cross, and said fervently, "He's a wonderful Saviour!”
“Yes, yes, I love the crucifix. Put it back, please. I hope it will help me to die well.”
“Not the crucifix," was the reply, "but the One who died on the cross, the Lord Jesus, He died to save you.”
The man looked bewildered, then his face brightened: "Oh, I see, not the crucifix but the One who died. He died for me. I see, sir, I see. I never understood it before.”
It was evident that faith had sprung up in his soul. Mr. Parker replaced the crucifix, offered a brief prayer, and left. In a few minutes he observed the body being wheeled out of the ward.
Telling me of it later, he exclaimed, "I knew that God thinks so much of the work of His Son that He will have every one in heaven who will give Him any excuse for taking them there!" It is blessedly true. Faith's look at the Crucified saves, even though it be faith of the feeblest kind.
“There is life in a look at the Crucified One,
There is life at this moment for thee;
Then look, sinner, look unto Him and be saved,
Unto Him who was ne led to the tree.”