Adam Clarke on Matthew 10:19

Take no thought how or what ye shall speak - Μη μεριμνησετε - Be not anxiously careful, because such anxiety argues distrust in God, and infallibly produces a confused mind. In such a state, no person is fit to proclaim or vindicate the truth. This promise, It shall be given you, etc., banishes all distrust and inquietude on dangerous occasions; but without encouraging sloth and negligence, and without dispensing with the obligation we are under to prepare ourselves by the meditation of sacred truths, by the study of the Holy Scriptures, and by prayer.

It shall be given you in that same hour what - This clause is wanting in the MSS. D and L, and several others, some versions, and several of the fathers: but it is found in Mar 13:11, without any various reading; and in substance in Luk 11:13.