Abu Nu’aym reported: Khalid ibn Ma’dan, may Allah have mercy on him, said, “If a door of good is open for one of you, let him rush to it. He does not know when it will be closed to him.”
Source: Ḥilyat al-Awliyā’ 5/211
عن أبي نعيم عَنْ خَالِدِ بْنِ مَعْدَانَ رحمه الله قَالَ إِذَا فُتِحَ لِأَحَدِكُمْ بَابُ خَيْرٍ فَلْيُسْرِعْ إِلَيْهِ فَإِنَّهُ لَا يَدْرِي مَتَى يُغْلَقُ عَنْهُ
5/211 حلية الأولياء وطبقات الأصفياء