What Paul solemnly affirms is how I yearn for you all with the affection of Christ Jesus. The verb translated yearn (epipotheō) means “to have a strong desire for someth[ing], with implication of need.” Paul regularly uses this verb to describe an intense desire for fellow believers (Rom 1:11; 2 Cor 9:14; 1 Thess 3:6; 2 Tim 1:4), and will do so later in the letter to describe Epaphroditus’s longing for the Philippians while he was with Paul (Phil 2:26). In the LXX of the Psalms it expresses a longing for God (42:1 [2x]), his courts (84:2), his word (119:20, 131) and his salvation (119:174). Paul uses this strong term to indicate the depth of his longing to be with the Philippians and experience in person their fellowship in the gospel. And again he emphasizes that he longs for all of them, not merely some.
He yearns for them with the affection of Christ Jesus. The word rendered affections (splanchnon) in the first sense refers to one’s inward parts such as the kidneys or intestines, but came by extension to refer to a person’s seat of emotions or a feeling itself. It “concerns and expresses the total personality at the deepest level.” This usage is similar to the way that we might speak of the heart; when we say someone feels sorrow in his heart, we do not mean sorrow in the physical organ that pumps blood throughout the body. Paul always uses this word in connection with fellow believers, including later in Philippians 2:1.
In the Gospels the related verb splanchnizomai repeatedly describes Jesus’ compassion for people (Matt 9:36; 14:14; 15:32; 20:34; Mark 1:41; 6:34; 8:2; Luke 7:13; 10:33). This observation is interesting in light of Paul describing his affection as being of Christ Jesus. While there are a number of different ways this expression could be understood, it most likely means “the affection that comes from Christ Jesus.” Paul longs for the Philippians with a deep-seated affection that comes from Jesus Christ himself as they experience fellowship in the gospel. As believers we experience the very same affection that Jesus Christ showed those he encountered, because Christ lives in us to experience and express that affection for others. “Paul’s deeply emotional expression of Christian affection in this verse is not primarily the sign of a gushing temperament, but of a gushing Christology!”
The power of the gospel is shown in the supernatural affection that it produces not only for Jesus Christ himself, but also for those who belong to Jesus Christ. This affection is deepened as believers experience fellowship in the gospel. People who have little or nothing in common on an economic, social, political or ethnic basis are brought together by the Holy Spirit in unified devotion to Christ and the advance of his gospel.
 Philo uses this verb to express a desire for virtue (Abr. 1:48) and God himself (Abr. 1:87).
 TDNT 7:555.
 As such the genitive indicates origin. Other possibilities include subjective (“affection that Jesus Christ has for you”) or possessive (“affection that belongs to Jesus Christ”).
 “In the meantime he instructs us by what rule the affections of believers ought to be regulated, so that, renouncing their own will, they may allow Christ to sit at the helm. And, unquestionably, true love can flow from no other source than from the bowels of Christ, and this, like a goad, ought to affect us not a little—that Christ in a manner opens his bowels, that by them he may cherish mutual affection between us”; see Calvin et al., Philippians, 30-31.
 “It is not Paul who lives within Paul, but Jesus Christ, which is why Paul is not moved by the bowels of Paul but by the bowels of Jesus Christ”; see Johann Albrecht Bengel, Charlton Thomas Lewis and Marvin Richardson Vincent, New Testament Word Studies (2 vols.; Grand Rapids: Kregel, 1971), 2:426. Compare the similar comment by Lightfoot: “The believer has no yearnings apart from his Lord; his pulse beats with the pulse of Christ; his heart throbs with the heart of Christ”; see Joseph Barber Lightfoot, Saint Paul’s Epistle to the Philippians (London: Macmillan and Co., Limited, 1898), 85.
Bockmuehl, Philippians, 65.