do what you are commanded...
do what you are commanded; if Allah please, you will surely find me of the patient ones.” So when they both submitted and he threw him down upon his forehead, and We called out to him (saying): “O Ibrahim! You have indeed proved the vision true; surely thus We reward the doers of good. Most surely this is a manifest trial” (37:102-106).
This manifest trial had taken place in the extreme old age of Ibrahim, because even the birth of Isma'il had taken place when Ibrahim had become very old, as Allah quotes him as saying: “Praise be to Allah, Who gave me in old age Isma'il and Ishaq; most surely my Lord is the Hearer of prayer” (14:39). And the imamah was given to him after these trials.
You give someone an order, or put him in a difficult situation, in order to find out his inner strength, his spiritual sublimity; thus you bring out his hidden qualities like obedience, bravery, generosity, chastity, knowledge, faithfulness (or their opposite traits); it is only then that you may say, “I have tested him”, “I have put him to trial”.
One cannot be tested except through action; it is the action which brings out the hidden qualities of a man, and not the word; words may lie but not the actions. Allah says: Surely We have tried them as We tried the owners of the garden... (68:17); ... Surely Allah will try you with a stream... (2:249). Now Allah says that He tried Ibrahim with certain words.
Of course, the word, “word”, has sometimes been used in the Qur'an for a substance, a corporeal being (instead of a talk or speech) as Allah says: ... a Word from Him whose name is the Messiah, 'Isa son of Maryam... (3:45). But this usage is based on the fact that 'Isa, like Adam, was created by a word from Allah as the Qur'an says: Surely the likeness of 'Isa is with Allah as the likeness of Adam; He created him from dust, then said to him: “Be”, and he was (3:59) .