The Greek text of Phil. 2:5-8 according to the Nestle-Aland 28th edition states,
5 Τοῦτο φρονεῖτε ἐν ὑμῖν ὃ καὶ ἐν Χριστῷ Ἰησοῦ, 6 ὃς ἐν μορφῇ θεοῦ ὑπάρχων οὐχ ἁρπαγμὸν ἡγήσατο τὸ εἶναι ἴσα θεῷ, 7 ἀλλ’ ἑαυτὸν ἐκένωσεν μορφὴν δούλου λαβών, ἐν ὁμοιώματι ἀνθρώπων γενόμενος· καὶ σχήματι εὑρεθεὶς ὡς ἄνθρωπος 8 ἐταπείνωσεν ἑαυτὸν γενόμενος ὑπήκοος μέχρι θανάτου, θανάτου δὲ σταυροῦ. NA28
which may be translated into English as,
5 Have this mindset in you which was also in Christ Jesus, 6 who, originally existing in the form of God, did not consider being equal to God something to be grasped, 7 but rather, he emptied himself when he took [the] form of a servant, when he was made in the likeness of men, and when he was found in manner as a man. 8 He humbled himself when he became obedient unto death, even the death of the cross.
In v. 5, the apostle Paul commands the Phillipians to "have this mindset in you which was also in Christ Jesus." The lemma φρονέω does not simply refer to the momentary act of thinking, but having a relatively permanent mindset or frame of mind. A few verses earlier, the apostle Paul also urged the Phillipians to “have the same mindset”1 and mentions “having the same one mindset.”2 He elaborates what constitutes this mindset in the next verse when he writes,
3 Let there be nothing after strife or vainglory, but rather, in humility, esteeming one another better than themselves. 4 Let not each man look on his own things, but also let each man [look on] the things of others.
3 μηδὲν κατ’ ἐριθείαν μηδὲ κατὰ κενοδοξίαν ἀλλὰ τῇ ταπεινοφροσύνῃ ἀλλήλους ἡγούμενοι ὑπερέχοντας ἑαυτῶν, 4 μὴ τὰ ἑαυτῶν ἕκαστος σκοπεῖτε, ἀλλὰ καὶ τὰ ἑτέρων ἕκαστος NA28
In vv. 2-3, there are some notable words:
v. 2:
- τὸ αὐτὸ φρονῆτε (“have the same mindset”)
- τὸ ἓν φρονοῦντες (“having the same one mindset”)
v. 3:
- κενοδοξίαν (n.; lemma κενοδοξία), meaning “empty pride; vain glory.”
- ταπεινοφροσύνῃ (n.; lemma ταπεινοφροσύνη), an abstract noun meaning “humility” or “humble-mindedness.”
- ἡγούμενοι (v.; lemma ἡγέομαι), meaning “to consider, esteem.”
The words on the left correlate to the words on the right:
+-------------------------+--------------------+
| τὸ αὐτὸ φρονῆτε (v. 2) | φρονεῖτε (v. 5) |
| τὸ ἓν φρονοῦντες (v. 2) | φρονεῖτε (v. 5) |
| ἡγούμενοι (v. 3) | ἡγήσατο (v. 6) |
| κενοδοξίαν (v. 3) | ἐκένωσεν (v. 7) |
| ταπεινοφροσύνῃ (v. 3) | ἐταπείνωσεν (v. 8) |
+-------------------------+--------------------+
Some may wish to assume the associations are mere coincidences, but I think otherwise.
The apostle Paul states that the Lord Jesus Christ “emptied himself” (ἑαυτὸν ἐκένωσεν). The verb ἐκένωσεν is conjugated in the aorist tense, indicative mood. It is followed by three aorist participles: (1) λαβών, (2) γενόμενος, and (3) εὑρεθεὶς. The action of each of these aorist participles is concurrent with the action of the aorist indicative verb. That is to say, the Lord Jesus Christ emptied himself:
- when he took the form of a servant (μορφὴν δούλου λαβών)
- when he was made in the likeness of men (ἐν ὁμοιώματι ἀνθρώπων γενόμενος)
- when he was found in the manner as a man (σχήματι εὑρεθεὶς ὡς ἄνθρωπος)
These participial clauses specify when the emptying occurred (which basically refers to the incarnation), but they don't tell us what the Lord Jesus Christ emptied himself of. That answer I believe comes from the word κενοδοξίαν in v. 3. The apostle Paul commanded the Philippians to “let there be nothing after strife or vainglory.” The word “vainglory” is translated from κενοδοξίαν, which basically comes from two words, κενός, meaning “empty,” and δόξα, meaning “glory.” It seems to me that the apostle Paul is contrasting the manner of the Philippians with that of the Lord Jesus Christ. The Philippians were conceited with a baseless self-pride or empty glory. On the other hand, the Lord Jesus Christ, who indeed had a legitimate basis for pride and glory, being equal to God the Father with whom he had glory before the world was,3 emptied himself of such glory upon his incarnation.
The apostle Paul also commands the Philippians to let there be things [done] “after humility.” On the other hand, the Lord Jesus Christ “humbled himself when he became obedient unto death, even the death of the cross.” Again, the aorist participles following the aorist indicative paints the action of the participle as concurrent with that of the verb. Therefore, the humiliation occurred during the crucifixion, or perhaps, culminated in the crucifixion.
Summary: The Lord Jesus Christ “emptied himself” when he incarnated, that is, (1) when he took the form of a servant, (2) when he was made in the likeness of men, and (3) when he was found in manner as a man. He emptied himself of the glory which he had with God the Father before the world was, not his divinity or deity.
Footnotes
1 Phil. 2:2: «τὸ αὐτὸ φρονῆτε»
2 ibid.: «τὸ ἓν φρονοῦντες»
3 John 17:5