She has some orphans’ wealth in trust, and it may be consumed by zakaah; is she sinning if she does not invest it?
Question

                A widow came to me and gave me a sum of money to keep as a trust, until she needed it. This money is just for her orphan children. I am afraid that it will be consumed by zakaah as our Messenger (peace and blessings of Allaah be upon him) said. Please note that she has not asked me to invest it. I do not know where to invest it. Is there any sin on me for that?.
Praise be to Allah.There is no 
    sin on you if you do not invest this money, because you have only taken it 
    to keep it as a trust. What you have to do is keep it safe, and give it to 
    its owner when she asks for it, because Allaah says (interpretation of the 
    meaning): 
“Verily, 
    Allaah commands that you should render back the trusts to those, to whom 
    they are due”
[al-Nisa’ 
    4:58]
And the 
    Prophet  (peace and blessings of Allaah be upon him) said: “Give the 
    trust to the one who entrusted it to you.” Narrated by al-Tirmidhi (1264) 
    and Abu Dawood (3534); classed as saheeh by al-Albaani in Saheeh 
    al-Tirmidhi. 
You should 
    advise this sister and explain to her that this wealth is subject to zakaah, 
    and tell her that zakaah may consume it if she does not invest it. 
We refer to 
    the hadeeth, “Whoever takes care of an orphan who has wealth, let him invest 
    it in trade and not leave it to be consumed by zakaah.” This was narrated by 
    al-Tirmidhi (641) and classed as da’eef by al-Albaani in Da’eef 
    al-Tirmidhi, but its meaning is sound and clear, because the orphan’s 
    wealth is like the wealth of any one else: if it reaches the minimum 
    threshold (nisaab) and one full hijri year has passed, zakaah is due on it. 
    If it is not invested, zakaah must be taken from it every year, which will 
    lead to it decreasing. 
This is 
    proven in the words of ‘Umar (may Allaah be pleased with him): “Do trade 
    with the orphan’s wealth so that it will not be consumed by zakaah.” 
    Narrated by al-Daaraqutni and al-Bayhaqi, who said: Its isnaad is saheeh. 
And Allaah 
    knows best.