It may be that Paul here has haunting his memory our Lord's words which we have just quoted; and, in any case, he is in beautiful accord with his brother Peter, who begins all the exhortations of his epistle with the words, 'Wherefore, girding up the loins of your mind, be sober, and set your minds perfectly upon the grace that is to be brought unto you at the revelation of Jesus Christ.' Peter, indeed, is not thinking of the soldier's belt, but he is, no doubt, remembering many a time when, in the toils of the fishing-boat, he had to tighten his robes round his waist to prepare for tugging at the oar, and he feels that such concentration is needful if a Christian life is ever to be sober, and to have its hope set perfectly on Christ and His grace.
II. The girdle is to be truth.
The question immediately arises as to whether truth here means objective truth—the truth of the Gospel, or subjective truth, or, as we are accustomed to say, truthfulness. It would seem that the former signification is rather included in the sword of the Spirit, which is the word of God, and it is best to regard the phrase 'with (literally "in") truth' here as having its ordinary meaning, of which we may take as examples the phrases, 'the unleavened bread of sincerity and truth'; 'love rejoiceth not in unrighteousness, but rejoiceth with the truth'; 'whom I love in truth.' Absolute sincerity and transparent truthfulness may well be regarded as the girdle which encloses and keeps secure every other Christian grace and virtue.
We do not need to go far to find a slight tinge of unreality marring the Christian life: we have only to scrutinise our own experiences to detect some tendency to affectation, to saying a little more than is quite true, even in our sincerest worship. And we cannot but recognise that in all Christian communities there is present an element of conventionalism in their prayers, and that often the public expression of religious emotions goes far beyond the realities of feeling in the worshippers. In fact, terrible as the acknowledgment may be, we shall be blind if we do not recognise that the average Christianity of this day suffers from nothing more than it does from the lack of this transparent sincerity, and of absolute correspondence between inward fact and outward expression. Types of Christianity which make much of emotion are, of course, specially exposed to such a danger, but those which make least of it are not exempt, and we all need to lay to heart, far more seriously than we ordinarily do, that God 'desires truth in the outward parts.' The sturdy English moralist who proclaimed 'Clear your mind of cant' as the first condition of attaining wisdom, was not so very far from Paul's point of view in our text, but his exhortation covered but a small section of the Apostle's.
This absolute sincerity is hard to attain, and still harder to retain. Hideous as the fact of posing or attitudinising in our religion may be, it is one that comes very easily to us all, and, when it comes, spreads fast and spoils everything. Just as the legionary's armour was held in its place by the girdle, and if that worked loose or was carelessly fastened, the breastplate would be sure to get out of position, so all the subsequent graces largely depend for their vigorous exercise on the prime virtue of truthfulness. Righteousness and faith will be weakened by the fatal taint of insincerity, and, on the other hand, conscious truthfulness will give strength to the whole man. Braced up and concentrated, our powers for all service and for all conflict will be increased. 'The bond of perfectness' is, no doubt, 'Love,' but that perfect bond will not be worn by us, unless we have girded our loins with truthfulness.
It may be that in Paul's memory there is floating Isaiah's great vision of the 'Branch' out of the stock of Jesse, on whom the Spirit of the Lord was to rest, and on whom it was proclaimed that faithfulness (or as it is rendered in the Septuagint, by the same phrase which the Apostle here employs, 'in truth') was to be the girdle of his reins; but, at all events, that which the prophet saw to be in the ideal Messiah, the Apostle sees as essential to all the subjects of that King.
III. Our truthfulness is the work of God's truth.
We have already pointed out that the expression in the text may either be taken as referring to the subjective quality of truthfulness, or to the objective truth of God as contained in the Gospel, but these two interpretations may be united, for the main factor in producing the former is the faithful use of the latter and an honest submission to its operation. The Psalmist of old had learned that the great safeguard against sin was the resolve, 'Thy word have I hid in my heart.' That word brings to bear the mightiest motives that can sway life. It moves by love, by fear, by hope: it proposes the loftiest aim, even to imitate God as dear children; it gives clear directions, and draws straight and plain the pilgrim's path; it holds out the largest promises, and in a measure fulfils them, even in the narrowest and most troubled lives. If we have made God's truth our own, and are faithfully applying it to the details of daily life and submitting our whole selves to its operation, we shall be truthful and shall instinctively shrink from all unreality. If we know the truth as it is in Jesus, and walk in it, that 'truth will make us free,' and if thus 'we are in Him that is true, even in His Son, Jesus Christ,' that truth abiding in us, and with us, for ever, will make us truthful. In a heart so occupied and filled there is no room for the make-believes which are but too apt to creep into religious experience. Such a soul will recoil with an instinct of abhorrence from all that savours of ostentation, and will feel that its truest treasure cannot be shown. It is our duty not to hide God's righteousness within our hearts, but it is equally our duty to hide His word there. We have to seek to make manifest the 'savour of His knowledge in every place,' but we have also to remember that in our hearts there is a secret place, and that 'not easily forgiven are they who draw back the curtains,' and let a careless world look in. It is not for others to pry into the hidden mysteries of the fellowship of a soul with the indwelling Christ, however it may be the Christian duty to show to all and sundry the blessed and transforming effects of that fellowship.
But God's truth must be received and its power submitted to, if it is to implant in us the supreme grace of perfect truthfulness. Our minds and hearts must be saturated with it by many an hour of solitary reflection, by meditation which will diffuse its aroma like a fragrant perfume through our characters, and by the habit of bringing all circumstances, moods, and desires to be tested by its infallible criterion, and by the unreluctant acceptance of its guidance at every moment of our lives. There are many of us who, in a real though terribly imperfect sense, hold the truth, but who know nothing, or next to nothing, of its power to make us truthful. If it is to be of any use to us, we must make it ours in a far deeper sense than it is ours now; for many of us the girdle has been but carelessly fastened and has worked loose, and because, by our own faults, we have not 'abode in the truth,' it has come to pass that there is 'no truth in us.' We have set before us in the text the one condition on which all Christian progress depends, and if by any slackness we loosen the girdle of truthfulness, and admit into our religious life any taint of unreality, if our prayers say just a little more than is quite true, and our penitence a little less, we shall speedily find that hypocrisy and trivial insincerity are separated by very narrow limits. God's truth in the Gospel cleanses the inner man, but not without his own effort, and, therefore, we are commanded to 'cleanse ourselves from all filthiness of flesh and spirit, perfecting holiness, in the fear of the Lord.'