An-Nisa · 4:9

9. Let those executors and guardians fear in the manner they would if they had died and left young, weak children behind them, fearing they would be ruined. Let them be mindful of orphans under their guardianship, not doing any wrong to them. So that Allah brings about others to treat well their own children after they die, as they treated the orphans well. Let whoever is present at the making of will, say what is right for the children, so that the heirs are not wronged in the will. Nor should the giver deprive himself of this good deed by not leaving a will.