He was a burning and a shining light - literally, “the burning and shining lamp” (or torch): - that is, “the great light of his day.” Christ is never called by the humble word here applied to John - a light-bearer - studiously used to distinguish him from his Master, but ever the Light in the most absolute sense. (See on Joh 1:6).
willing for a season - that is, till they saw that it pointed whither they were not prepared to go.
to rejoice in his light - There is a play of irony here, referring to the hollow delight with which his testimony tickled them.