This is about knowing the love of Christ. That is the reasoning of the apostle: it starts in verse 16.
The breadth of the love of Christ points to the salvation of people from all nations. It is not a love which is confined to the Jewish people, or to any one category of person. It is not confined only to those who some people imagine have the good sense to choose Christ. Nobody will choose Christ; nobody will forsake their sin, not a single person will repent and believe. That is the trouble with the human race: people are unwilling to repent and believe. Before you get to whether people are able or not, the massive fact is that they are unwilling to believe. The scope of the love of Christ includes people who would never have turned to him. He comes by irresistible grace in the power of the Spirit and overwhelms the heart and humbles the mind and causes people to fall on their knees and repent and turn – not just ‘nice sinners’, but the very worst of sinners, people whose sins he detests and yet his love is so great he will save them. Its breadth covers all our needs. We need not only forgiveness, we need righteousness to be given to us, his righteousness. We need power and life to be poured into us.
And its length – that suggests the duration of his blessing. When he saves, he saves forever. We shall never be lost if truly saved, the perseverance of the saints. Our blessedness will last throughout the everlasting ages of eternity. His love covers us no matter how long the time spent in sin, no matter how long we resisted the overtures of grace; he saves old sinners as well as young sinners. Saul of Tarsus was certainly not a young man when Christ saved him. He had sinned away many years in pride and opposition to Christ. When Christ spoke to Nicodemus, a leader of the Jews, a Pharisee, he was an old man.
Then the depth of the love of Christ. Whoever would have imagined that he would come down from heaven to the depths of humiliation and the indescribable agony of Calvary for creatures like us? He went to hell for us. He descended into hell, not literally. He entered our hell on Calvary’s cross when all our hell and the punishment that we deserved in hell was poured out upon him – the hideous cost, the agony, the despair he felt in separation from the Father, our eternal weight of separation.
What does the height suggest? The wisdom of his love, the plan of salvation which enables Christ the second person of the Trinity, and God the Father, and God the Holy Spirit to exercise their judgement and to punish sin and yet at the same time, to forgive those who would be saved. He said to the disciples, I go to prepare a place for you. He was preparing that place even as he died on Calvary’s cross, as well as when he ascended into heaven. On Calvary’s cross as he bore the agony, he also planned the blessedness and all that he would give to us now and in the everlasting ages. He planned the husband he would give you, the wife he would give you, the family he would give you, the place he would post you to, the blessings and the prayers he would answer.