What is the ruling on speaking about worldly and religious matters in the mosque, as long as they are not forbidden?

The first thing for someone entering the mosque is to engage in prayer, remembrance (dhikr), and supplication (du'a). It is permissible to engage in permissible conversations in the mosque, concerning both worldly and afterlife matters, as long as there is no raising of voices, disturbing those praying and remembering Allah, or engaging in activities explicitly prohibited by texts, such as buying, selling, or announcing lost property. The evidence for this is the hadith of Jabir ibn Samurah in Sahih Muslim: "The Messenger of Allah (peace and blessings be upon him) would not leave his prayer place where he prayed Fajr until the sun rose. When it rose, he would stand up. Jabir said: 'And they used to converse, and they would talk about matters of the time of Jahiliyyah, and they would laugh and smile.'"