Revelation 7:9-17 is a visual text. It is written so that the reader can envision a grand scene. It is the First Reading appointed for All Saints Sunday in the Year of Matthew, and as such it is a wonderful text to proclaim the good news to all who have come through "the great ordeal." It will be the preacher's great privilege to do so.
(The following questions are not meant to be exhaustive, but only to provide a way to answer the fundamental concerns of Law and Gospel preaching around the function of the Word. This is crucial since the way the Word functions should, in large part, inform the function of the sermon. For more on this method and on Law and Gospel preaching in general, see my brief guide, Afflicting the Comfortable, Comforting the Afflicted, available from wipfandstock.com or amazon.)
1. How does the Word function in the text? The Word functions here almost exclusively as Gospel, beginning in the 10th verse, when the multitude declares, "Salvation belongs to our God who is seated on the throne, and to the Lamb!" There are also multiple other places in this text where God's work overcoming sin, death, and the devil are being proclaimed.
2. How is the Word not functioning in the text? The Word is not functioning as Law in this text at all, although there are several allusions to our need of the Gospel. When the elder identifies the great multitude as those who have come out of the great ordeal, those who once hungered, thirsted, were subjected to scorching heat, and wept tears, we are reminded of our need for a Savior.
3. With whom are you identifying in the text? By the very nature of the text we are invited to identify with the seer who is given this vision. We are invited to stand with the elder and marvel at the scene before us, the saints triumphant, singing their praises to God.
4. What, if any, call to obedience is there in this text? This text could be understood as an implied call to obedience. We who have been caught up into God's embrace could do no better than to find ourselves in regular praise of the God of our salvation.
5. What Law/Gospel couplet is suggested by this text? Since this passage is functioning almost entirely as Gospel, we will have to use our imagination to create some couplets. A few possibilities: enduring a great ordeal/rescued by God; unprotected in the storm/sheltered; hungry/fed; thirsty/filled.
6. Exegetical work: One cannot but help notice that these verses regarding "a great multitude that no one could count, from every nation", come immediately after verses announcing that "those who were sealed" were 144,000 out of the twelve tribes of Israel. It is the juxtaposition of a great uncounted throng from all tribes and nations next to a very precise number of people, all of the house of Jacob. What do we make of this? Primasius, 6th century African bishop, had this to say: "By the sign of the sacred number he signifies the multitude of the elect, 'whom God foreknew and predestined to be conformed to the image of his Son.' For those who come from the nations are made to be Israel and so by right are called sons of Abraham, not by flesh but by faith in that seed which is Christ, the cornerstone, of whom the apostle said, 'He is our peace, who has made us both one...'". (Ancient Christian Commentary on Scripture, NT, vol. XII, p. 110-111). Kittel's article on the Greek term thlipsis, makes the case that "the ordeal" described here is "not merely factual, but necessary" for Christians. An example are the words of Paul and Barnabas following their persecution in Lystra: "It is through many persecutions that we must enter the kingdom of God." (Acts 14:22). Kittel goes on to say, "Sufferings are a test whether the Christian will champion the Gospel at the risk of his (sic) life or not, which means finally whether he will understand his own life in terms of its possibilities or in terms of the divine promise and the possibilities opened up by it." (Theological Dictionary of the NT, vol. III, p. 147f).
7. How does the Crossings Community model work with this text? Robin Morgan, in a 2014 analysis, begins with "the great ordeal" and argues that our bondage to sin ensures that we will do all we can to avoid the great ordeal. The word of the Gospel is that Christ endured "The Great Ordeal", indeed the Greatest Ordeal, in order to overcome all that would separate us from Christ. So we have hope even amidst the great ordeal. See Morgan's analysis archived under the reference at crossings.org/text-study.
Blessings on your proclamation!