Jesus had been WITH the disciples during His earthly ministry, but by the Spirit He would come to be IN them. On earth He had only been able to be in one place at one time, but, by the Spirit’s indwelling, the Church would take the presence of the Lord simultaneously to the uttermost parts of the earth.
“Even in acts of worship our strength is in the Lord. Consider prayer. Would we pray? Where will we find topics for our prayers? Alas, ‘We know not what we should pray for as we ought’ (Rom 8:26). Let us alone, and we will soon pray ourselves into some temptation or other, and beg for the very thing God knows we should not have. To protect us, then, God puts words in our mouths (Hos 14:2). But without some heart-heating affections to thaw the tap, the words will freeze on our lips. We may search in vain the corridors of our own hearts and the drafty corners of our souls. We will not find a spark upon our own hearth, unless it is some strange fire of our own desires, which will not do. No, the fire that thaws the iciness of the heart must come from heaven – a gift from God, who is ‘a consuming fire’ (Heb 12:29).
“First the Spirit stretches Himself upon the soul, as the prophet on the child; then the soul will begin to kindle and put forth some heavenly heat in its affections. At last the Spirit melts the heart, and prayer flows from the lips of the believer as naturally as tears from the eyes. And though the saint is the speaker, the author of the prayer is God. So we see that both the strength to pray and the prayer itself are from God.”