While he was on the pulpit, he said, "I have withheld from you a hadith that I heard from the Messenger of Allah ﷺ, fearing that you would scatter away from me. Then it occurred to me that I should narrate it to you, so that each person may choose for himself what he sees fit. I heard the Messenger of Allah ﷺ say, 'Standing guard for one day in the cause of Allah is better than a thousand days spent anywhere else.'"
حدثنا الحسن بن علي الخلال حدثنا هشام بن عبد الملك حدثنا الليث بن سعد حدثني أبو عقيل زهرة بن معبد عن أبي صالح مولى عثمان قال
وهو على المنبر يقول إني كتمتكم حديثا سمعته من رسول الله ﷺ كراهية تفرقكم عني ثم بدا لي أن أحدثكموه ليختار امرؤ لنفسه ما بدا له سمعت رسول الله ﷺ يقول رباط يوم في سبيل الله خير من ألف يوم فيما سواه من المنازل
Its isnad is sahih. Nasai also reported it, 6/39, hadith 3171 (jihad, chapter on the merit of ribat), from 6/39, through the hadith of Layth bin Saad, with the same content. Ibn Hibban graded it sahih, hadith 1592, as did Hakim, 2/68, 143, and Dhahabi agreed with him.