But in all things It is the singular number that is made use of by Paul, but is the neuter gender; the expression, therefore, is equivalent to omni negotio, (in every matter,) for (prayer) and (supplication) are feminine nouns. In these words he exhorts the Philippians, as David does all the pious in Psalm 55:22, and Peter also in 1-Peter 5:7, to cast all their care upon the Lord. For we are not made of iron, [1] so as not to be shaken by temptations. But this is our consolation, this is our solace -- to deposit, or (to speak with greater propriety) to disburden in the bosom of God everything that harasses us. Confidence, it is true, brings tranquillity to our minds, but it is only in the event of our exercising ourselves in prayers. Whenever, therefore, we are assailed by any temptation, let us betake ourselves forthwith to prayer, as to a sacred asylum. [2] The term requests he employs here to denote desires or wishes. He would have us make these known to God by prayer and supplication, as though believers poured forth their hearts before God, when they commit themselves, and all that they have, to Him. Those, indeed, who look hither and thither to the vain comforts of the world, may appear to be in some degree relieved; but there is one sure refuge -- leaning upon the Lord. With thanksgiving As many often pray to God amiss, [3] full of complaints or of murmurings, as though they had just ground for accusing him, while others cannot brook delay, if he does not immediately gratify their desires, Paul on this account conjoins thanksgiving with prayers. It is as though he had said, that those things which are necessary for us ought to be desired by us from the Lord in such a way, that we, nevertheless, subject our affections to his good pleasure, and give thanks while presenting petitions. And, unquestionably, gratitude [4] will have this effect upon us -- that the will of God will be the grand sum of our desires.

Footnotes

1 - "Car nous ne sommes de fer ni d'acier (comme on dit) ne si insensibles;" -- "For we are not of iron nor steel, as they say, nor so insensible."

2 - "Comme a vne franchise;" -- "As to a privilege."

3 - "Autrement qu'ils ne doyuent;" -- "Otherwise than they ought."

4 - "La recognoissance des benefices de Dieu;" -- "Gratitude for God's benefits."

Be careful for nothing - That is, be not anxious or solicitous about the things of the present life. The word used here - μεριμνᾶτε merimnate - does not mean that we are to exercise no care about worldly matters - no care to preserve our property, or to provide for our families (compare 1-Timothy 5:8); but that there is to be such confidence in God as to free the mind from anxiety, and such a sense of dependence on him as to keep it calm; see the subject explained in the notes on Matthew 6:25.
But in everything - Everything in reference to the supply of your wants, and the wants of your families; everything in respect to afflictions, embarrassments, and trials; and everything relating to your spiritual condition. There is nothing which pertains to body, mind, estate, friends, conflicts, losses, trials, hopes, fears, in reference to which we may not go and spread it all out before the Lord.
By prayer and supplication - The word rendered "supplication" is a stronger term than the former. It is the mode of prayer which especially arises from the sense of "need," or "want" - from δέομαι deomai, "to want, to need."
With thanksgiving - Thanksgiving connected with prayer. We can always find something to be thankful for, no matter what may be the burden of our wants, or the special subject of our petitions. When we pray for the supply of our wants, we may be thankful for that kind providence which has hitherto befriended us; when we pray for restoration from sickness, we may be thankful for the health we have hitherto enjoyed, and for God's merciful interposition in the former days of trial, and for his goodness in now sparing our lives; when we pray that our children and friends may be preserved from danger and death, we may remember how often God has interposed to save them; when, oppressed with a sense of sin, we pray for pardon, we have abundant cause of thanksgiving that there is a glorious way by which we may be saved. The greatest sufferer that lives in this world of redeeming love, and who has the offer of heaven before him, has cause of gratitude.
Let your request be made known unto God - Not as if you were to give him information, but to express to him your wants. God needs not to be informed of our necessities, but he requires that we come and express them to him; compare Ezekiel 36:37. "Thus saith the Lord God, I will yet for this be inquired of by the house of Israel to do it for them."

Be careful for nothing - Μηδεν μεριμνατε· Be not anxiously solicitous; do not give place to carking care, let what will occur; for anxiety cannot chance the state or condition of any thing from bad to good, but will infallibly injure your own souls.
By prayer and supplication - God alone can help you; he is disposed to do it, but you must ask by prayer and supplication; without this he has not promised to help you.
By prayer - solemn application to God from a sense of want.
Supplication - continuance in earnest prayer. With thanksgiving, for innumerable favors already received; and for dangers, evils, and deaths turned aside. And let your souls be found in this exercise, or in the disposition in which this exercise can be performed, at all times, on all occasions, and in all places.

(6) Be careful for nothing; but in every thing by prayer and supplication with (f) thanksgiving let your requests be made known unto God.
(6) The third is, that we are not too anxious for anything, but with sure confidence give God thanks, and desire from him whatever we have need of, that with a quiet conscience we may wholly and with all our hearts submit ourselves to him.
(f) So David began very often with tears, but ended with thanksgiving.

Be careful for nothing,.... This must be understood not in the most extensive sense, but with a limitation and restriction. There are many things that saints are to be careful for, as men and Christians; they are to be careful of their bodies, as well as of their souls; of the health of them, which is to be preserved by all lawful means, and not exposed to unnecessary danger; and for their families, to provide things honest for them, proper food and raiment, and the necessaries of life; for whoever does not do that, denies the faith, and is worse than an infidel; and even for the things of this world in a moderate way, using all diligence and industry in obtaining them; men ought to be careful to discharge the duties of their calling in civil life, and to care and concern themselves for the honour of God, the interest of religion, and the support of the Gospel; and that they offend not God, by sinning against him: but the carefulness the apostle speaks of, is an anxious solicitude for worldly things, an immoderate concern for the things of life, arising from diffidence, or negligence, of the power, providence, and faithfulness of God: saints should not be anxiously, or in a distressing manner concerned for the things of this world, but be content, whether they have less or more; nor be over much pressed with what befalls them, but should cast their care upon the Lord, and carry every case to him, and leave it there:
but in everything. The Syriac and Ethiopic versions render it, "in every time": always, constantly, every day, as often as there is opportunity, and need requires. The Vulgate Latin and Arabic versions join it with the following clause, "in every prayer and supplication"; but the grammatical construction of the words will not admit of such a version; it is best to understand it of every thing, or case, which should be brought to God; whether it be of a temporal or spiritual kind, relating to body or soul, to ourselves or others, to our families, relations, and acquaintance, the church, or the world:
by prayer and supplication: which may include all sorts of prayer, mental or vocal, private or public, ordinary or extraordinary, and every part of prayer: prayer may design petition, or asking for good things that are wanted; and "supplication", a deprecating of evils that are feared; though these two are often used together for the same thing, for prayer in general: which ought always to be accompanied
with thanksgiving; for mercies received; for a man can never come to the throne of grace, to ask for grace and mercy, but he has mercies to bless God for, and so to do is very acceptable to God; nor can a person expect to succeed in the enjoyment of future mercies, when he is not thankful for past and present ones: in this manner therefore, at all times, upon every occasion, in a way of humble petition and supplication, joined with thankfulness for all favours,
let your requests be made known to God; not to men; fly not to an arm of flesh, but to God, to him only, and that in the most private mariner, as not to be known by men; and put up such requests, as there may be reason to hope and believe God will "know" and approve of; such as are agreeable to his will, to the covenant of his grace, and the declaration of his word: use familiarity with God, tell him as you would do a friend, freely and fully, all your case, pour out your souls and your complaints before him. This God would have his people do, and he expects it from them; and though he knows all their wants, and what are their desires before they express them, yet he will seem not to know them, or take any notice of them, until they open them to him in some way or other; either by vocal prayer, or mental; by ejaculations, or sighs and groans, by chattering as a crane or a swallow, all which he understands: and be the case made known in what way or manner soever, with ever so much weakness, so be it, it is made known, it is enough, it shall be regarded and not despised.

Translate, "Be anxious about nothing." Care and prayer are as mutually opposed as fire and water [BENGEL].
by prayer and supplication--Greek, "by the prayer and the supplication" appropriate to each case [ALFORD]. Prayer for blessings; and the general term. Supplication, to avert ills; a special term, suppliant entreaty (see on Ephesians 6:18).
thanksgiving--for every event, prosperity and affliction alike (1-Thessalonians 5:18; James 5:13). The Philippians might remember Paul's example at Philippi when in the innermost prison (Acts 16:25). Thanksgiving gives effect to prayer (2-Chronicles 20:21), and frees from anxious carefulness by making all God's dealings matter for praise, not merely for resignation, much less murmuring. "Peace" is the companion of "thanksgiving" (Philippians 4:7; Colossians 3:15).
let your requests be made known unto God--with generous, filial, unreserved confidence; not keeping aught back, as too great, or else too small, to bring before God, though you might feel so as to your fellow men. So Jacob, when fearing Esau (Genesis 32:9-12); Hezekiah fearing Sennacherib (2-Kings 19:14; Psalm 37:5).

Be anxiously careful for nothing - If men are not gentle towards you, yet neither on this, nor any other account, be careful, but pray. Carefulness and prayer cannot stand together. In every thing - Great and small. Let your requests be made known - They who by a preposterous shame or distrustful modesty, cover, stifle, or keep in their desires, as if they were either too small or too great, must be racked with care; from which they are entirely delivered, who pour them out with a free and filial confidence. To God - It is not always proper to disclose them to men. By supplication - Which is the enlarging upon and pressing our petition. With thanksgiving - The surest mark of a soul free from care, and of prayer joined with true resignation. This is always followed by peace. Peace and thanksgiving are both coupled together, Colossians 3:15.