One word, and not only the shortest but the best. So the best dua according to Rasulullah(SAW).
Abbas(RA), the uncle of Rasulullah(SAW), came to Rasulullah(SAW) and said, teach me something so I can ask Allah. Rasullah(SAW) said one word “Sal lila al aafiyah Ask Allah al aafiyah”. I waited a few more days then I came back to Rasulullah(SAW) and said Ya Rasulullah(SAW) teach me a dua to ask Allah with. So he said “O dear uncle, O Abbas ask Allah al aafiyah in the dunya and in the aakhirah. Subhanallah! what is al aafiyah? If you are healthy you have aafiyah, if you have enough wealth you have aafiyah, you have peace of mind at home you have aafiyah. you have righteous children’s you have aafiyah and you are guided you have aafiyah”. So aafiyah compasses all that and especially when you ask aafiyah in the Dunya and the akhirah. A Man came to Rasulullah(SAW) and said “ya Rasulullah(SAW) what is the best dua?” Rasulullah(SAW) said ” Salilah al aafiyah wal fuafat fid Dunya wal akhira Ask Allah al aafiyah and the muaafaat”. The difference between these two is that aafiyah is for yourself like the things we mentioned before and muaafaat is from the harm of others. The same person came the next day and asked ” ya Rasulullah(SAW) what is the best dua?”. He repeated the same thing. The next day he came again and asked the same question then Rasulullah(SAW) said ” ya rajul if Allah gave you aafiyah in the Dunya and in the akhirah you are the most successful.
So my brother and sisters one word “Allahumma Inni Asaluka al aafiyah”. When can you do it in your sujood, before the tasleem or anytime. As a matter of fact, one of the sayings of the morning and the saying of the evening as Rasulullah(SAW) used to say “Allahumma Inni Asaluka al afwa wal aafiyah”.