Gr. merimnaō, “to be anxious” (see on Matt. 6:25). “Careful” formerly meant “full of care.” Paul’s admonition prohibits the painful anxiety that is inevitable in those who are dependent on themselves in the midst of life’s difficulties. It is possible to sink below this anxiety in mere levity and thoughtlessness or to rise above it by “casting all your care upon him; for he careth for you” (1 Peter 5:7). The thought of the nearness of the coming of the Lord should help us to keep free from worldly anxieties, and to be forbearing in our relations with others. See on Matt. 6:33, 34; 1 Peter 5:7.

This removes all excuse for unbelieving anxiety. There is nothing that in any way concerns the peace of the Christian that is too small for God to notice, just as there is nothing too great for Him to care for. He knows what we need. He wants us to have everything that is for our good. Then why should we be burdened with cares which may be laid on Him?

The apostle now shows why the Christian need not be worried over the affairs of this life: through prayer, he may discuss all his needs with God.

 The two words “prayer” and “supplication” also occur together in Eph. 6:18; 1 Tim. 2:1; 5:5. It appears that “prayer” is used as a general word, covering the idea of prayer in its widest meaning. “Supplication” seems to refer to prayer for some particular object or need (see on Phil. 1:4).

This is in positive contrast to the “nothing” in the previous phrase.

 We do not bring our requests to God simply to inform Him concerning our needs. He knows our necessities before we ask (see on Matt. 6:8; see GC 525).

 “Thanksgiving” is a necessary accompaniment of prayer, and ought never to be absent from our devotions. It helps to remind us of past mercies and prepares us to receive further blessings. Paul himself sets an example of constant thankfulness (see on ch. 1:3).