AbulQasim ﷺ said: When one of you is in the sun (Shams)--Makhlad's version has "fay'"--and the shadow withdraws from him so that he is partly in sun and partly in shade, he should get up.
أَبُو الْقَاسِمِ ﷺ إِذَا كَانَ أَحَدُكُمْ فِي الشَّمْسِ وَقَالَ مَخْلَدٌ فِي الْفَىْءِ فَقَلَصَ عَنْهُ الظِّلُّ وَصَارَ بَعْضُهُ فِي الشَّمْسِ وَبَعْضُهُ فِي الظِّلِّ فَلْيَقُمْ