Sayyiduna Wathilah bin al-Asqa' (may Allah be pleased with him) narrates that the Prophet (peace and blessings be upon him) said: "A man should not wipe his forehead until he has finished his prayer, but there is no harm in wiping the sweat from his temples, for the angels continue to pray for mercy for him as long as the mark of prostration (i.e. dust and the like) remains between his eyes (i.e. on his forehead)."
Imam al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains Ayyub bin Mudrik, who is a kadhdhab (liar).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2761