“If you have run with the footmen.” In Jeremiah 12:1-4, Jeremiah has been speaking. The speaker now changes to God, but without any introduction such as “Then Yahweh said.” The reader has to pick up the change from the content of what is said.
“horses.” Jeremiah has been dealing with some very difficult situations, but they are “men” compared to the situations in store in his future, which God sees coming, and those future difficult people and situations are the “horses” (horses were the fast and powerful animals of the time). If we have trouble maintaining our trust in God and positive attitude when things are somewhat bad, how will we do if things get really difficult? We cannot be so connected to the things we enjoy in this life, including our hopes and dreams for here on earth, that we become discouraged and dejected if we lose them or never see them realized. God makes no promises for our prosperity here on earth, but He promises to be with us always and reward us for our faithfulness to Him.