The heading of the psalm tells us that its date is the very beginning of Saul's persecution, when 'they watched the house to kill' David, and he fled by night from the city. There is a certain correspondence between the circumstances and some part of the picture of his foes here which makes the date probable. If so, this is one of David's oldest psalms, and is interesting as showing his faith and courage, even in the first burst of danger. But whether that be so or not, we have here, at any rate, the voice of a devout soul in sore sorrow, and we may well learn the lesson of its twofold utterance. The man, overwhelmed by calamity, betakes himself to God. 'Upon Thee, O my Strength! will I wait, for God is my defence.' Then, by dint of _waiting_, although the outward circumstances keep just the same, his temper and feelings change. He began with, 'Deliver me from my enemies, O Lord! for they lie in wait for my soul.' He passes through 'My Strength! I will wait upon Thee,' and so ends with 'My Strength! I will sing unto Thee.' We may then throw our remarks into two groups, and deal for a few moments with these two points--the waiting on God, and the change of waiting into praise. Now, with regard to the first of these--the waiting on God--I must notice that the expression here, 'I will _wait_,' is a somewhat remarkable one. It means accurately, 'I will watch Thee,' and it is the word that is generally employed, not about our looking up to Him, but about His looking down to us. It would describe the action of a shepherd guarding his flock; of a sentry keeping a city; of the watchers that watch for the morning, and the like. By using it, the Psalmist seems as if he would say--There are two kinds of watching. There is God's watching over me, and there is my watching for God. I look up to Him that He may bless; He looks down upon me that He may take care of me. As He guards me, so I stand expectant before Him, as one in a besieged town, upon the ramparts there, looks eagerly out across the plain to see the coming of the long-expected succours. God 'waits to be gracious'--wonderful words, painting for us His watchfulness of fitting times and ways to bless us, and His patient attendance on our unwilling, careless spirits. We may well take a lesson from His attitude in bestowing, and on our parts, wait on Him to be helped. For these two things--vigilance and patience--are the main elements in the scriptural idea of waiting on God. Let me enforce each of them in a word or two.