According to Louw-Nida, the adjective πιστὸς has the potential meaning: "pertaining to being trusted - ‘faithful, trustworthy, dependable, reliable.’"
Compare 1 Peter 4:19.
1 Corinthians 4:2 (Greek): ὧδε λοιπὸν ζητεῖται ἐν τοῖς οἰκονόμοις ἵνα πιστός τις εὑρεθῇ.
Paul's use of πιστός in 1 and 2 Corinthians:
1 Corinthians 1:9-πιστὸς ὁ θεὸς δι' οὗ ἐκλήθητε εἰς κοινωνίαν τοῦ υἱοῦ αὐτοῦ Ἰησοῦ Χριστοῦ τοῦ κυρίου ἡμῶν.
1 Corinthians 4:17-Διὰ τοῦτο ἔπεμψα ὑμῖν Τιμόθεον, ὅς ἐστίν μου τέκνον ἀγαπητὸν καὶ πιστὸν ἐν κυρίῳ, ὃς ὑμᾶς ἀναμνήσει τὰς ὁδούς μου τὰς ἐν Χριστῷ Ἰησοῦ, καθὼς πανταχοῦ ἐν πάσῃ ἐκκλησίᾳ διδάσκω.
1 Corinthians 7:25-Περὶ δὲ τῶν παρθένων ἐπιταγὴν κυρίου οὐκ ἔχω, γνώμην δὲ δίδωμι ὡς ἠλεημένος ὑπὸ κυρίου πιστὸς εἶναι.
1 Corinthians 10:13-πειρασμὸς ὑμᾶς οὐκ εἴληφεν εἰ μὴ ἀνθρώπινος· πιστὸς δὲ ὁ θεός, ὃς οὐκ ἐάσει ὑμᾶς πειρασθῆναι ὑπὲρ ὃ δύνασθε, ἀλλὰ ποιήσει σὺν τῷ πειρασμῷ καὶ τὴν ἔκβασιν τοῦ δύνασθαι ὑπενεγκεῖν.
2 Corinthians 1:18-πιστὸς δὲ ὁ θεὸς ὅτι ὁ λόγος ἡμῶν ὁ πρὸς ὑμᾶς οὐκ ἔστιν Ναί καὶ Οὔ·
2 Corinthians 6:15-τίς δὲ συμφώνησις Χριστοῦ πρὸς Βελίαρ, ἢ τίς μερὶς πιστῷ μετὰ ἀπίστου;