The Hebrew נֶפֶשׁ sometimes functions like a personal pronoun when pronominal suffixes are appended to it. It could also be used as emphasis, like a reflexive pronoun.
Therefore, in Gen. 27:4, the Hebrew phrase בַּעֲבוּר תְּבָרֶכְךָ נַפְשִׁי בְּטֶרֶם אָמוּת could simply be translated as "so that I may bless you before I die" or even "so that I myself may bless you before I die." If this be the case, there isn't a substantial difference between a blessing which includes נֶפֶשׁ and a blessing which lacks it.
Brown-Driver-Briggs (p. 660) states,
- The נפשׁ as the essential of man stands for the man himself: a. paraphrase for pers. pron. especially in poetry and ornate discourse, 70 times; (1) נַּפְשִׁי = me: אל תבא נפשׁי Gn 49:6 let me not enter (poem in J ); תָּמֹת נ׳ מות ישׁרים Nu 23:10 let me die , etc. (poem); תָּמֹות נַפְשִׁי Ju 16:30 ( J ); אמרה נפשׁי La 3:24 I say . (2) נַפְשְׁךָ = thee: לְאֻמִּים תַּחַת נַפְשֶׁ˜ךָ Is 43:4 peoples instead of thee; אָֽמְרוּ לְנַפְשֵׁךְ 51:2 3. (3) נַפְשֹׁו = he: תלין נפשׁו בטוב ψ 25:13 he will not dwell in good circumstances . (4) נַפְשֵׁנוּ = we: מִפַּת יֹוקְשִׁים נַפְשֵׁנוּ כְּצִפֹּור נִמְלְטָה ψ 124:7 . (5) נַפְשָׁם = they, them: נַפְשָׁם בַּשְּׁבִי הָלָ˜כָה Is 46:2 they are gone into captivity; אוי לנפשׁם Is 3: 9. b. = reflexive, self , 53 times: אסר על נפשׁ bind oneself Nu 30: 3, 5 (×2), 6 , 7 , 8 , 9 , 10 , 11 , 12 ; לְעַנֹּת נ׳ Nu 30:14 to afflict oneself . (1) נַפְשִׁי = myself: לא אדע נ׳ Jb 9:21 Ct 6:12 I know not myself . (2) נַפְשְׁךָ = thyself: שׁמר נ׳ Dt 4:9 keep thyself . (3) נַפְשֹׁו = himself: אהב כנ׳ 1 S 18: 1, 3 ; 20:17 loved as himself . (4) נַפְשָׁהּ = herself: צדּקה נ׳ Je 3:11 justified herself . (5) נַפְשָׁם = themselves: הציל נ׳ deliver themselves Is 47:14 Ez 14:1 4, 20 . (6) נַפְשְׁכֶם , נַפְשֹׁתֵיכֶם = yourselves: אַל־תַּשִּׁאוּ נ׳ Je 37:9 deceive not yourselves , also 42:20 ; 44:7 ; ענּה נ׳ Lv 16:2 9, 31 ; 23:27 , 32 Nu 29:7 ( P ); נשׁמרתם לנ׳ Dt 4:15 Jos 23:11 ( D ). (7) נַפְשֹׁותֵינוּ = ourselves: על נ׳ Je 26:19 against ourselves . c. = person of man, individual, 144 times, first in D ; especially in H , P , and kindred writers: (1) c. אָדָם : נ׳ אדם Lv 24:17 opp. נ׳ בהמה 24:18 (both H ), and so נ׳ אדם human persons Nu 31:3 5, 40 , 46 ( P ) 1 Ch 5:21 Ez 27:1 3. Elsewhere without אדם : נ׳ ברכה Pr 11:25 one who blesses; נ׳ רְמִיָּה Pr 19:15 idle person; נ׳ תחת נ׳ person in place of person , Jb 16:4 ; על נ׳ כפּר Ex 30:1 5, 16 Nu 15:2 8; 31:50 (all P ) Lv 17:11 ( H ). • (2) נפשׁ = person, any one: Dt 24: 7; 27:25 Pr 28:17 Ez 18:4 (×3) 33: 6; elsewhere only H P: Lv 2:1 ; 4:2 , 27 ; 5:1 , 2 , 4 , 15 , 17 , 21 ; 7:18 , 20 , 21 , 25 , 27 ; 23:29 , 30 (×2) Nu 5: 6, 15:27 , 30 ; 19:22 ; 31:19 , 28 ; 35:11 , 15 , 30 (×2) Jos 20:3 , 9 (all P ), Lv 17:10 , 12 , 15 ; 20:6 (×2) 22: 6, 11 (all H ); הַהִוא מן נכרתה הנ׳ that person shall be cut off from: only in Gn 17:14 Ex 12:1 5, 19 ; 31:14 Lv 7:20 , 21 , 27 Nu 9:1 3; 15:30 , 31 ; 19:13 , 20 (all P ), Lv 19:8 ; 22:3 (both H ). • (3) נפשׁ coll. for persons , in enumerations: Dt 10:22 Jos 10:2 8, 30 , 32 , 35 , 37 (×2), 39 ; 11:11 (all D ) Je 43:6 ; 52:29 , 30 (×2) Ez 22:2 5; elsewhere only Gn 12:5 ; 46:15 , 18 ,
Also see Gesenius, p. 560, Section (5) on נֶפֶשׁ.
References
Brown, Francis; Driver, S. R.; Briggs, Charles A. A Hebrew and English Lexicon of the Old Testament. Oxford: Clarendon Press, 1906.
Gesenius, Heinrich Friedrich Wilhelm. Hebrew and Chaldee Lexicon to the Old Testament Scriptures. Trans. Tregelles, Samuel Prideaux. London: Bagster, 1857.
