If thou hast run with the footmen. — The prophet is compelled to make answer to himself, and the voice of Jehovah is heard in his inmost soul rebuking his impatience. What are the petty troubles that fall on him compared with what others suffer, with what might come on himself? The thought is not unlike that with which St. Paul comforts the Corinthians (1 Corinthians 10:13), or what we find in Hebrews 12:4. The meaning of the first clause is plain enough. The man who was wearied in a foot-race should not venture (as Elijah, e.g., had done, 1 Kings 18:46) to measure his speed against that of horses. The latter (“the swelling of Jordan”) suggests the thoughts of the turbid stream of the river overflowing its banks in the time of harvest (Joshua 3:15; 1 Chronicles 12:15). In Zechariah 11:3, however, the same phrase (there translated “the pride of Jordan”) is used apparently in connection with the lions and other beasts of prey that haunted the jungle on its banks (Jeremiah 49:19; Jeremiah 50:44), and that may be the thought here. Commentators differ, and there are no data for deciding. In any case, there is no need for the interpolated words of the English Version. The sentence should run, “In a land of peace thou art secure (i.e., it is easy to be tranquil when danger is not pressing). What wilt thou in the swelling (or, amid the pride) of Jordan?
Jeremiah 12:5
5 If thou hast run with the footmen, and they have wearied thee, then how canst thou contend with horses? and if in the land of peace, wherein thou trustedst, they wearied thee, then how wilt thou do in the swelling of Jordan?