The following is from a sermon by John Wesley.
And where no creature is, still God is there. The presence or absence of any or all creatures makes no difference with regard to him. He is equally in all, or without all. Many have been the disputes among philosophers whether there be any such thing as empty space in the universe; and it is now generally supposed that all space is full. Perhaps it cannot be proved that all space is filled with matter. But the Heathen himself will bear us witness, Jovis omnia plena: “All things are full of God.” Yea, and space exists beyond the bounds of creation (for creation must have bounds, seeing nothing is boundless, nothing can be, but the great Creator), even that space cannot exclude Him who fills the heaven and the earth…
Indeed this very expression, “Do not I fill heaven and earth?” (the question being equal to the strongest affirmation), implies the clearest assertion of God’s being present everywhere and filling all space; for it is well known, the Hebrew phrase “heaven and earth,” includes the whole universe; the whole extent of space, created or uncreated, and all that is therein.
Nay, and we cannot believe the omnipotence of God, unless we believe his omnipresence; for, seeing, as was observed before, nothing can act where it is not, — if there were any space where God was not present, he would not be able to do anything there. Therefore, to deny the omnipresence of God implies, likewise, the denial of his omnipotence. To set bounds to the one is undoubtedly to set bounds to the other also.
Indeed, wherever we suppose him not to be, there we suppose all his attributes to be in vain. He cannot exercise there either his justice or mercy, either his power or wisdom. In extra-mundane space, (so to speak) where we suppose God not to be present, we must, of course, suppose him to have no duration; but as it is supposed to be beyond the bounds of the creation, so it is beyond the bounds of the Creator’s power. Such is the blasphemous absurdity which is implied in this supposition…
In particular: If there is not a word in your tongue, not a syllable you speak, but he “knoweth it altogether;” how exact should you be in “setting a watch before your mouth, and in keeping the door of your lips!” How wary does it behove you to be in all your conversation; being forewarned by your Judge, that “by your words you shall be justified, or by your words you shall be condemned!” How cautious, lest “any corrupt communication,” any uncharitable, yea, or unprofitable discourse, should “proceed out of your mouth;” instead of “that which is good to the use of edifying, and meet to minister grace to the hearers!”
Yea, if God sees our hearts as well as our hands, and in all places; if he understandeth our thoughts long before they are clothed with words, how earnestly should we urge that petition, “Search me, O Lord, and prove me; try out my reins and my heart; look well if there be any way of wickedness in me, and lead me in the way everlasting!” Yea, how needful is it to work together with him, in “keeping our hearts with all diligence,” till he hath “cast down imaginations,” evil reasonings, “and everything that exalteth itself against the knowledge of God, and brought into captivity every thought to the obedience of Christ!”
On the other hand, if you are already listed under the great Captain of your salvation, seeing you are continually under the eye of your Captain, how zealous and active should you be to “fight the good fight of faith, and lay hold on eternal life;” “to endure hardship, as good soldiers of Jesus Christ;” to use all diligence, to “war a good warfare,” and to do whatever is acceptable in his sight! How studious should you be to approve all your ways to his all-seeing eyes; that he may say to your hearts, what he will proclaim aloud in the great assembly of men and angels, “Well done, good and faithful servants!”
In order to attain these glorious ends, spare no pains to preserve always a deep, a continual, a lively, and a joyful sense of his gracious presence. Never forget his comprehensive word to the great father of the faithful: “I am the Almighty” (rather, the All-sufficient) “God; walk before me, and be thou perfect!” Cheerfully expect that He, before whom you stand, will ever guide you with his eye, will support you by his guardian hand, will keep you from all evil, and “when you have suffered a while, [he] will make you perfect, will stablish, strengthen, and settle you;” and then “preserve you unblameable, unto the coming of our Lord Jesus Christ!” [from Sermon 111, “On the Omnipresence of God”; source]