A.T. Robertson Commentary Luke 17:14

"And when he saw them, he said unto them, Go and show yourselves unto the priests. And it came to pass, as they went, they were cleansed." — Luke 17:14 (ASV)

As they went (εν τω υπαγειν αυτους). Favourite Lukan idiom of εν with articular infinitive as in 17:11 and often.