This is from the Loeb collection of private papyri. Thanks to .@graham_claytor, here’s a link to the text on line
B.G.U. 7.1680 (CE 2nd Century?=Trismegistos 30955)
“Isis sends her mother the most greetings. I make a prayer for you each day before lord Sarapis and the gods who are with him.
I want to tell you that I made it safely and well to Alexandria in four days. I send greetings to my sister and her children, and Elouath and his wife, as well as Diokorous and her husband and son and Tamalis and her husband and son, and Hêron and Ammonarion and her children and her husband and Sanpat and her children. If Aiôn wants to join the army, have him come. For everyone is joining the army.
I pray for you and everyone in the house to be well.
Your daughter, Isis
Ἶσεις Θερμουθίῳ τῇ μητρὶ πλεῖστα χαίρειν. τὸ προσκύνημά σου ποιῶ καθ᾿ ἑκάστην ἡμέραν παρὰ τῷ κυρίῳ [Σ]αράπιδι καὶ τοῖς συννάοις θεοῖς. γεινώσκειν σε θέλω ὅτι εὖ καὶ καλῶς γέγονα εἰς Ἀλεξάνδρειαν ἐν τέσσαρσι ἡμέραις. ἀσπάζομαι τὴν ἀδε[λ]φήν μο[υ] καὶ τὰ παιδία καὶ Ἐλουᾶθ καὶ τὴν γυναῖκα αὐτοῦ καὶ Διοσκοροῦν καὶ τὸν ἄνδρα αὐτῆς καὶ τὰ παιδία καὶ Τ[ά]μαλιν καὶ τὸν 7ἄνδρα αὐτῆς καὶ τὸν υἱὸν καὶ Ἥρωνα καὶ Ἀμμωνάριον καὶ τὰ παιδία αὐτῆς καὶ τὸν ἄνδρα καὶ Σανπὰτ καὶ τὰ παιδία αὐτῆς. καὶ ἐὰν θελήσῃ Ἀΐων στρατεύσασθαι, ἐρχέσθω· στρατεύονται γὰρ πάντες. ἐρρῶσθαι ⟦σε⟧ ὑμᾶς εὔχομαι πανοικί.
Verso: – – – π](αρὰ) Ἴσειτος θυγατρός.
Here’s a picture of the letter (again, thanks to @graham_claytor)