Definitions:

1. To rejoice together, to share in another's joy, with the dative depending on syn, together, in composition.

References:

1. Lk. 1:58; 15:6,9; 1 Cor. 12:26; Phil. 2:17,8; Sept.: Gen. 21:6 in the middle voice.

Definitions: Truth, reality; the unveiled reality lying at the basis of and agreeing with an appearance; the manifested, the veritable essence of matter.

1. Conduct conformed to the truth, integrity, probity, virtue, a life conformed to the precepts of the gospel. In Rom 2:8 and 1 Cor 13:6, aLE-theia stands in opposition to adiKIa, unrighteousness, wrong.

References:

1. Eph. 4:21; 1 Tim. 6:5; James 5:19; 3 John 3,4,12; Sept.: Ps. 119:30; Prov. 28:6; Is. 26:10.

Ps. 146:5--Blessed (maKArios) is he whose helper is the God of Jacob, whose hope (elPIS) is in the Lord his God: 6 who made heaven, and earth, the sea, and all (PANta) things in them: who keeps (phyLASsonta) truth (aLE-theian) for ever: 7 who executes judgment for the wronged (adikouMEnois): who gives food to the hungry. The Lord looses the fettered ones: 8 the Lord gives wisdom (soPHOI) to the blind:
The Lord sets up the broken down: the Lord loves (agaPA) the righteous (diKAIous): the Lord preserves (phyLASsei) the strangers (tous prose-LYtous); 9 he will relieve (anaLE-psetai) the orphan and widow: but will utterly remove the way of sinners. (Brenton LXX)
Alt.: Happy is he who ... 6 ... who keeps faith forever; ... 8 ... the Lord makes those who are bent stand straight; ... 9 The Lord watches over the stranger; He gives courage to the orphan and widow (JPS 1985)
Alt.: ... 6 ... who remains faithful forever. 7 He upholds the cause of the oppressed (NIV)
Alt.: ... 6 ... He remains loyal forever. ... 8 ... The Lord loves those who do right. (NCV)
Alt.: ... 6 ... the One keeping trueness to time indefinite, 7 the One executing judgment for the defauded ones, the One giving bread to the hungry ones (NWT)

Lk. 1:58--[Mary's] neighbors and relatives heard that the Lord had shown her great mercy (Eleos), and they shared her joy (syNEchairon auTE-). (NIV)
Alt.: ... and they rejoiced with her. (RSV)
Alt.: ... heard that Jehovah had magnified his mercy to her, and they began to rejoice with her. (NWT)
Alt.: The word spread quickly to her neighbors and relatives of how kind the Lord had been to her, and everyone rejoiced. (LB)
Alt.: ... heard how wonderfully good the Lord had been to her ... (TEV)

St. John Chrysostom, Homily 33:  but also, what is much greater, "rejoiceth with the truth." "She feels pleasure," saith he, "with them that are well spoken of," as Paul saith, "Rejoice with them that rejoice, and weep with them that weep." (Romans chapter 12, verse 15)

Adam Clarke:  But rejoiceth in the truth] alhqeia? Every thing that is opposite to falsehood and irreligion. Those who are filled with the love of God and man rejoice in the propagation and extension of Divine truth-in the spread of true religion, by which alone peace and good will can be diffused throughout the earth. And because they rejoice in the truth, therefore they do not persecute nor hinder true religion, but help it forward with all their might and power.

Geneva Notes:  Rejoices at righteousness in the righteous. For by "truth" the Hebrews mean "righteousness".

John Gill's Exposition of the Bible:  but rejoiceth in the truth; in the truth of the Gospel, and the success of it; such an one can do nothing against it, but for it, will buy it at any rate, but sell it upon no account whatever; and he rejoices greatly when he sees any walking in it, and agreeably to it; for truth, as it stands opposed to iniquity or unrighteousness, may signify an upright, holy, and righteous conversation, a conversation becoming the Gospel of Christ, which that teaches, and by which it is adorned; now a gracious soul desires this in itself, and delights to see it in others.

John W. Gregson:  "Rejoiceth in the truth (sugchairei aletheia) or rejoices with truth;... Those who have love in their hearts are never happy with unrighteousness or evil, for it is opposed to truth. ... It rejoices in the truth; it is happy when others are happy. "Our sources of news tell us that the public will lap up bad and unsavory news. Christian love finds no appeal or joy in this, but instead rejoices in the Lord, who is truth, and in every evidence of Him seen in others" (Sunday School Times, October 12, 1963, p. 9).

Matthew Henry:  It rejoiceth in the truth, is glad of the success of the gospel, commonly called the truth, by way of emphasis, in the New Testament; and rejoices to see men moulded into an evangelical temper by it, and made good. It takes no pleasure in their sins, but is highly delighted to see them do well, to approve themselves men of probity and integrity. It gives it much satisfaction to see truth and justice prevail among men, innocency cleared, and mutual faith and trust established, and to see piety and true religion flourish.

Jamieson, Fausset, & Brown:  rejoiceth in the truth--rather, "rejoiceth with the truth." ... but rejoices when the truth rejoices; sympathizes with it in its triumphs (2Jo 4). See the opposite (2Ti 3:8), "Resist the truth." So "the truth" and "unrighteousness" are contrasted (Ro 2:8). "The truth" is the Gospel truth, the inseparable ally of love (Eph 4:15; 2Jo 12). The false charity which compromises "the truth" by glossing over "iniquity" or unrighteousness is thus tacitly condemned (Pr 17:15).

B.W. Johnson:  but does rejoice with the truth in its triumphs.

Mark Heber Miller:  (Love) rejoices with the truth.

This phrase is variously rendered: KNX: rejoices at the victory of truth; WEY: joyfully sides with the truth; WMS: always glad when truth prevails; BECK: happy with the truth.

Suppose we hear something evil about another, something slanderous, but later it is made clear that such an untruth was a lie or misunderstanding? If one harbors envy or jealousy there may be a tendency not to rejoice over this truth. Love causes one to rejoice that the real truth is made known, rather than seeking another untruth about the individual.

Robertson's Word Studies:  {But rejoiceth with the truth} (suncairei de tei aleqeiai). Associative instrumental case after sun- in composition. Truth personified as opposed to unrighteousness (#2Th 2:12; Ro 2:8). Love is on the side of the angels. Paul returns here to the positive side of the picture (verse #4) after the remarkable negatives.

BT Internet:  sugcairw, rejoice with, rejoice together

'joyfully celebrate'

ajlhqeia, a", f., truth, reality; ejn, aj., truly

"Genuine love, as I argue as my main theis in Interpreting God and the Postmodern Self, alone decentres the power of 'interests' of the self and of its peer group, and in recentering them in the Other (primarily in God, but also in the other person) disengages from self-interest. Only now can truth emerge as disengaged from a power agenda. True disinterested integrity is free to seek truth, without anxiety about what it helps or hinders in one's personal agenda. Love, Paul says, has discovered integrity: As Nygren constantly declares, because it is disinterested and creative of value. It delights in truth... As Karl Rahner observes, the person who has placed everything in the hands of God has no need to fear, or to hide from, the truth. For God already knows it and has accepted the believer as he or she is." --Thistleton

The Theologian: The Internet Journal for Integrated Theology:  [The Corinthians] are to rejoice not merely with the "good" but with the "truth"--wherever that truth is found, even in an "opposing" faction.

Bill Turner:  Love rejoices with the truth, it rejoices when the truth prevails.

After a succession of powerful negative aspects of love, Paul turns again to the positive aspects of love. "Love rejoices in the truth," "sunchairei de tei aletheiai;" it sides with the truth, and rejoices when truth sanctifies the lives of Christians. Jn.17v17. Truth, as well as love, is here personified and powerfully compared with unrighteousness. 2Thes.2v12. Instead of finding pleasure in compiling and gloating over a person's faults, the loving Christian rejoices in their spiritual victories and attainments, and will do all they can to promote further spiritual well-being. It may be difficult to rejoice in truth when it shows us our deficiencies, but it is essential if we are to make spiritual progress. Jn.8v32. 7v17. 14v21. 2Tim.3v8.

Vincent's Word Studies:  Rejoiceth in the truth (sugcairei th alhqeia). Rev., correctly, rejoiceth with. Truth is personified as love is. Compare Psalm lxxxv. 10.