“Therefore if there is any consolation in Christ, if any comfort of love, if any fellowship of the Spirit, if any affection and mercy, fulfill my joy by being like-minded, having the same love, being of one accord, of one mind” (Philippians 2:1-2).

“If” (ei) does not express doubt.  It is used as a rhetoric device to point out truth.  It is as if Paul is asking, “Are these things taught in Scripture?”  The reader is forced to admit, “Certainly, they are.”  The word “if” can be used in clauses where the reality of the condition is understood (Galatians 3:29 cf. 3:26-27; Colossians 3:1 cf. 2:12).

The following things are mentioned: (1) Consolation in Christ [exhortation (ASV), encouragement (NASB, ESV)].  Does the Bible teach that those in Christ (Christians) are to console, exhort, and encourage one another.  It certainly does.  Christians are to “exhort one another daily… lest any… be hardened through the deceitfulness of sin” (Hebrews 3:13).  Christians are to “consider one another in order to stir up love and good works” (Hebrews 10:24).  (2) Comfort of love [consolation (ASV, NASB)].  Does the Bible teach that Christians are to lovingly comfort, and console one another.  It certainly does.  Christians comfort one another (1 Thessalonians 4:18; 2 Corinthians 1:3-4).  Christians are taught, “Warn those who are unruly, comfort the fainthearted, uphold the weak, be patient with all” (1 Thessalonians 5:14).  (3) Fellowship of the Spirit [participation (ESV).   The definite article is not before “spirit” in the original language.  However, I have no objection to understanding this to be referring to the Holy Spirit].  Fellowship (koinonia) refers to “A relation(ship) between individuals which involve a common interest and a mutual, active participation in that interest and in each other” (Vincent); “association, communing fellowship, close relationship… participation, sharing in something” (BAG).  Does the Holy Spirit teach that Christians are to have a close relationship with one another?  It certainly does.  Christians are to be united, working together as different members of one body (Romans 12:4-5; 1 Corinthians 12:14-23); (4) Affection and mercy [bowels and mercy (KJV); tender mercies and compassion (ASV); affection and compassion (NASB); affection and sympathy (ESV)].  The first word (splanchnon) refers to “bowels, intestines (heart, lungs, liver, etc.)… in the Greek poets from Aeschylus  down the bowels were regarded as the seat of the more violent passions, such as anger… but by the Hebrews as the seat of the tenderer affections, especially kindness, benevolence, compassion” (Thayer); “affections, of heart” (Vine’s).  The second word (oiktirmos) refers to “the viscera, which was thought to be the seat of compassion… compassion, pity, mercy” (Thayer); “pity, compassion for the ills of others” (Vine’s).  Does the Bible teach that Christians are to care for one another?  It certainly does.  Christians are taught to “rejoice with those who rejoice, and weep with those who weep” (Romans 12:15).  This word (oiktrimos) is closely connected with being longsuffering and forgiving (cf. Colossians 3:12-13).

Since it is the case that these things are taught in the Bible, Paul tells the brethren to so love one another.  He says that such would cause him great joy.

Brethren, since it is the case that these things are taught in the Bible, let us so love one another.  Such behavior gives me great joy.