As one of our great teachers, little remembered now said, 'Let me take my personal salvation for granted'--and what? and 'be idle?' No; 'and _work_ from it.' Ay, brethren! a Christian is not to be for ever asking himself, 'Am I a Christian?' He is not to be for ever looking into himself for marks and signs that he is. He _is_ to look into himself to discover sins, that he may by God's help cast them out, to discover sins that shall teach him to say with greater thankfulness, 'What a redemption this is which I possess!' but he is to base his convictions that he is God's child upon something other than his own characteristics and the feebleness of his own strength. He is to have 'joy in the Lord' whatever may be his sorrow from outward things. And I believe that if Christian people would lay that thought to heart, they would understand better how the natural operation of the Gospel is to make them glad, and how rejoicing in the Lord is a Christian duty. III. And now with regard to the other thought that still remains to be considered, namely, that rejoicing in the Lord is a source of strength,--I have already anticipated, fragmentarily, nearly all that I could have said here in a more systematic form. All gladness has something to do with our efficiency; for it is the prerogative of man that his force comes from his mind, and not from his body. That old song about a sad heart tiring in a mile, is as true in regard to the Gospel, and the works of Christian people, as in any other case. If we have hearts full of light, and souls at rest in Christ, and the wealth and blessedness of a tranquil gladness lying there, and filling our being; work will be easy, endurance will be easy, sorrow will be bearable, trials will not be so very hard, and above all temptations we shall be lifted, and set upon a rock. If the soul is full, and full of joy, what side of it will be exposed to the assault of any temptation? If the appeal be to fear, the gladness that is there is an answer. If the appeal be to passion, desire, wish for pleasure of any sort, there is no need for any more-the heart is _full_. And so the gladness which rests in Christ will be a gladness which will fit us for all service and for all endurance, which will be unbroken by any sorrow, and, like the magic shield of the old legends, invisible, impenetrable, in its crystalline purity will stand before the tempted heart, and will repel all the 'fiery darts of the wicked.'