That he proved faithful and trustworthy is shown by what Paul wrote about him some years later.
وَفِي تِلْكَ ٱلرِّسَالَةِ عَيْنِهَا ،‏ قَالَ لَهُ :‏ « خُذْ مَرْقُسَ وَأْتِ بِهِ مَعَكَ ،‏ فَهُوَ نَافِعٌ لِي لِلْخِدْمَةِ » .‏