Adam Clarke on Luke 17:13

They lifted up their voices - They cried with one accord - they were all equally necessitous, and there was but one voice among them all, though ten were engaged in crying at the same time. As they were companions in suffering, they were also companions in prayer. Prayer should be strong and earnest, when the disease is great and inveterate. Sin is the worst of all leprosies; it not only separates those to whom it cleaves from the righteous, but it separates them from God; and nothing but the pitying heart and powerful hand of Christ Jesus can set any soul free from it.